ABOUT SPF RECORD CHECK. Use this page to validate or check your SPF records. An SPF Validator is a tool used to authenticate email messages and prevent email spoofing. A colon-separated list of names. The first is just using a domain and selector separated by a colon and the second option is using the host/name format of the record. Directives are the first part of an SPF record syntax. While our DMARC analyzer and other free tools have you covered at the beginning of your journey, EasyDMARC’s platform truly. Hackers use domains without SPF configuration. How to avoid mail delivery issues by configuring SPF and DMARC. Note: If you use MTA-STS, it is recommended to also use SMTP TLS reporting, we have a validator for SMTP TLS. Basic Advanced Sender IP Address Sender Address Test SPF Tools Check your SPF policy for syntax errors to discover problems prior publishing. As an integral part of email cybersecurity, SPF enables the receiving mail server to check whether incoming email comes from a domain authorized by that domain’s administrators. Email Deliverability Status. All Tools; Email; Network; Website; DNS; NEW! My Favorite Tools; Delivery Center; mx. Use our DMARC checker to see if a domain has a valid policy. Step 4. A Safe SPF record is an SPF record after all. It will also show you a warning when your DNS records are misconfigured. Scott Kitterman’s SPF Record Testing Tool. DKIM selector (optional) Use this free SPF wizard to generate the SPF records for your domains. In client mode, espoofer works as an email client to test validation in sending services. 6. home Home Check MX HAR Analyzer Log Analyzer Log Analyzer 2 Messageheader Useragent Additional Tools Encode/Decode Screen. Identify who may be responsible. outlook. Also called a canonical name records, they act as aliases, pointing to another DNS name. Check each email address on your mailing list with three-step email validation. Directives are the first part of an SPF record syntax. · On Fri, 19 Apr 2013 16:10:49 +0000,. An advanced, custom PHP code checker that searches your code for common, hard to find typos and mistakes; includes a syntax check. The defined flags are as follows: “y” – this domain is testing DKIM (test mode) “s” – verifiers MUST check for domain alignment (strict mode) Utilize dmarcian's DKIM Inspector to see if the public part of your DKIM signature has been implemented correctly in the DNS of your domain. The Sender Policy Framework (SPF) is an email authentication protocol designed to prevent email spoofing, a common technique used in phishing attacks and email spam. See domain-based open and bounce rates. It will display “Open” next to each port that receives traffic. A. 3600. – Name/Host: @. Web Tools. For example, “pct=25” tells receivers to apply the “p=” policy 25% of the time against email that fails the DMARC check. Example of what the output may look like. This set of tools are core to DMARC and Email Delivery. To revisit, DMARC consents a sender’s domain to indicate that their. Discover any problems with your SPF record. The SPF lookup analyzes registered TXT records in real time. A DNS query of type TXT should result in 1 TXT record that starts with v. com offers an online check tool to validate your SPF settings sending an e-mail message: 1. Validate with the Kitterman SPF Record testing tool: Enter the domain name m365info. Click Start Authentication next to the verified email domain you want to work with. An SPF record checker looks up the record for a queried domain, displays any. SPF is a standard email authentication method. To check the TXT records for a certain domain name on Windows, follow these steps: Open a command prompt by navigating to Start → 'Type here to search' → 'cmd' → Open. While you test email addresses, you can also use the free list analysis tool as a bounce checker. 28. Hi, can some one tell what is the difference between these websites? Using MS show that the domain sinon. MAIL FROM The "MAIL" command initiates transfer of mail and identifies the sender. SPF stands for Sender Policy Framework, which is a widely used email authentication protocol . The validation outcome is the SPF Lookup Tree that you can expand to find main and additional lookups, like the following: Look Up SPF Records by Agari. By authenticating sender's mail server, the SPF protects senders and. Kitterman# SPF query tool by Kitterman allows you to quickly validate if the SPF record exists for a domain. Look Up SPF Records just shows the valid record and provides some general insights,. com ~all. This test will lookup an SPF record for the queried domain name, display the SPF Record (if found), and run a series of diagnostic tests (SPF Validation) against the record,. Free website reputation checker tool lets you scan a website with multiple website reputation/blocklist services to check if the website is safe and legit or malicious. home Home Check MX HAR Analyzer Log Analyzer Log Analyzer 2 Messageheader Useragent Additional Tools Encode/Decode Screen Recorder info help. Currently, this version must be “spf1” as it’s recognized by the widest range of mail exchange servers. To perform the DKIM record lookup for a particular selector. 2 images and logos to BIMI-compatible. RealSender. SPF specifies the mail servers that are allowed to send email for your domain. The tool validates whether the credit card is genuine or not. Deliverability is like operating a ham radio – it’s been around a while but most people don’t know how to use it. For example, you might. But for it to work, your own or your e-mail service provider's setup may need to be adjusted. Microsoft users can get started with one click. A typical SPF record example ‘s syntax would look like this: v=spf1 include:_spf. Learn more ; Format messages according to the Internet Message Format standard . Verifying is important before contacting new recipients to avoid bounces and protect your sender's reputation. Set the type to TXT and enter your SPF record in the right column (substitute your server’s IP address. Open the console or command line on your computer. 3. DKIM, SPF, SpamAssassin Email Validator. 3%. For Gmail and other mailbox providers requiring a VMC, make sure you have a valid VMC. A DNS lookup is done directly against the root servers (or TLD Servers). com. From the Admin console Home page, go to AppsGoogle WorkspaceGmail. Valid DMARC record. dmarcian developed SPF flattening as an experiment to work around the DNS lookup limit. If you don't set up DKIM and instead allow Microsoft 365 to use the default DKIM configuration for your domain, DMARC may fail. This test will lookup an SPF record for the queried domain name, display the SPF Record (if found), and run a series of diagnostic tests (SPF Validation) against the record, highlighting any errors. You may use our SPF Validator tool to verify SPF records for your domain name. As a domain health checker, it comprehensively analyzes your SPF, DKIM, DMARC, and BIMI records, ensuring your domain is secure and protected against. Enter the domain URL, select the desired DNS record type, or choose 'ALL' to fetch all DNS records. Use our free Email Analyzer to see if your emails are passing SPF and DKIM. This library validates that a string is of the form [email protected] domain. To check an SPF record, there is the SPF record checker, or SPF record validator/tester, which checks if an SPF record is published on your domain, and if its syntax is correct. To check an SPF record, there is the SPF record checker, or SPF record validator/tester, which checks if an SPF record is published on your domain, and if its. DKIM selector (optional)How to Implement BIMI in 5 Easy Steps. tw does not have SPF but using Kitterman show that that domain has more than one entry! * the same occurs to pap. The Domain Owner requests no specific action be taken regarding delivery of messages. Free SPF record generator is an online tool to create and/or validate SPF DNS records to protect your domain from email scams and phishing. Follow the next few steps : If you don’t have an existing SPF record, publish the following SPF record in your domain’s DNS: v=spf1 include:_netblocks. Address record. DKIM validator. To run a DMARC record check, enter the domain in question, and it will return the DMARC record on the domain if any, from a DNS lookup. com. The Mimecast SPF validator can also pre-validate and update before it is applied to a record to prevent post-update issues. DMARC record check enables an organization to forward domain-level policies and preferences for reporting, message validation, and disposition and permits it to take extreme measures against emails that defy authentication checks like SPF or. 4 states that evaluation of an SPF policy may not exceed 10 terms that require DNS lookups. The CNAME lookup is done directly against the domain's authoritative name server, so changes to CNAME Records should show up instantly. Specifically, the sending of emails via unauthorized mail servers is to be prevented. Then check here to see the results. See the exact SMTP "conversation" to help you troubleshoot email issues. DKIM Tools To create/generate a DKIM record, there is the DKIM record generator, or DKIM record creator/builder, which takes a domain and a selector, and returns a DKIM. You invest for better email marketing ROI. SPF records support several kinds of whitelist token: ip4:123. With the SPF Analyzer you analyze a manually submitted SPF record of a domain for errors, security risks and authorized IP addresses. If you want to learn more about SPF, see our SPF knowledge base article. RFC 3596 [2] IPv6. _domainkey. ARC Overview. Test your email for SPF, DKIM, DMARC, blacklistings, and more. An SPF record starts with a “v,” indicating the SPF version used. Open the DMARC Check & DMARC Lookup tool. Then the tool will check the validity of the SPF record and notify if the record passes the validation with pySPF. Please note: As you're not logged, checking DNS will not affect the timeline in your account. Then it calls the pySPF SPF record retreival function (dns_spf) and reports the results. validate_email() - Optional Arguments By default, the validate_email() method accepts only one argument - the string representation of the email address that needs to be validated, but can accept a few other keyword arguments:. The Main Domain label identifies the domain that your hosting provider used to create this account. SPF records are a good start for sysadmins hoping to reduce forgery, but if not implemented carefully, they can actually cause outages. If you don't know your mail server's address, start with a MX Lookup. High five! Your SPF record is valid, but. If you are using multiple Third-Party services for your various email strategies, it can be easy to exceed this limitation. In fact, I am not sure. Check your DMARC, SPF & DKIM for free. Use SPF Record Generator to create an SPF record. By adding an SPF record to your Domain Name System (DNS), you can provide a public list of senders that are approved to send email from your domain. Send an e-mail to check-auth@verifier. The SPF Validator is a tool that helps validate SPF records and troubleshoot issues. The SPF or Sender Policy Framework is intended to prevent spoofing of sender addresses in emails. google. Find your SPF record and uncover any errors that could adversely impact email delivery. Perform the following steps. Mail Server Test Tool is a free online tool to validate the configuration of mail servers. Mimecast offers a free DKIM record checker that can validate DKIM records. Others simply use “ default “. Use this tool to lookup and verify a DKIM DNS TXT record and determine its public key length to detect the use of weak cryptographic DKIM keys (less than 1024 bits). SPF is designed to help prevent spoofing, but there are spoofing techniques that SPF cannot protect against. com. You may use our Reverse DNS tool to lookup IP to Domain name mapping. Email has security standards to control which senders are allowed to send email for your domain. Step 6. Add DMARC to disallow unauthorized use of your email domain to protect people from spam, fraud. Learn more about Spam Solver. DKIM Key Checker. Email authentication, or validation, is a collection of techniques aimed at providing verifiable information about the origin of email messages by validating the domain ownership of any message transfer agents (MTA) who participated in transferring and possibly modifying a message. An SPF record check, sometimes called an SPF validator, determines if an SPF record is valid by looking up the DNS record for a domain. Step 5. [[svg_display_link]] Note:-[[generated_note_svg]] View in Dark Mode. com or Opens a new window / to check that everything is setup ok. Enter any valid domain or IP address to check the response headers, and click on the "Check HTTP Headers" button. hasRecords((err, hasRecords) => console. Google Workspace domains typically use “ google ”. In general, an SPF record is defined using a type of TXT record (not to be confused with the legacy SPF file type record). The first check an SPF validator performs is verifying if an SPF record is present. Our award-winning application helps organizations of all sizes reduce email security risk as efficiently and effectively as possible. Global. An email verifier, or email checker, is a tool to validate that an email address exists and can receive emails. DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol designed to give email domain owners the ability to protect their domain from unauthorized use, also known as email spoofing. It is intended to mitigate the weaknesses that exist in both DKIM and SPF. And you'll have a chronological history of your results. SPF record lengthThe logo referenced by a Brand Indicators for Message Identification (BIMI) record must be in a specific SVG Tiny Portable/Secure (SVG P/S) format. 8+ by Joshua Tauberer. Depending on the capabilities of the Mail Receiver, this can mean "place. Delivery Center enables you to monitor email delivery information unlike any other. SPF/DKIM/DMARC deployment tools Whether you are just getting started, or a seasoned professional, DMARCLY's free deployment tools will aid you in. ABOUT EMAIL DELIVERABILITY. Our platform is designed in a step-forward manner. However, instead of focusing on the part of the address that goes after the. SPF (Sender Policy Framework) record: This record is used to specify which mail servers are authorized to send email on behalf of a domain. See how Emma uses PowerMTA to scale mail volumes efficiently with a minimal resources and rapid growth. This is useful for verifying the end-to-end functionality of your DKIM and SPF configuration, as well as your. Click “+ Add Row” to create a new record. Send up to 10,000 notifications every month, for free. The records shows the recipient that you are authorized to send an email with this domain. Click on View from the menu bar. Receivers use these policies to determine if a sender is to be trusted. By sending an email to our DMARC tester, we will analyze your DMARC setup and visualize how an email server will validate the SPF, DKIM, and DMARC. Setting up SPF and DKIM on your domain is also known as "domain authentication" or "authenticate your domain". Validate and Check Your SPF Syntax. A valid SPF TXT record contains the following elements:. For Gmail and other mailbox providers requiring a VMC, make sure you have a valid VMC. Award winning e-mail security and monitoring software for Microsoft Exchange and IIS. All tools. The defined flags are as follows: “y” – this domain is testing DKIM (test mode) “s” – verifiers MUST check for domain alignment (strict mode) Utilize dmarcian's DKIM Validator diagnostic tool to validate the content of DKIM records, and learn why that is important. Interpreting email headers. Step 3: Set up DKIM for your custom domain. Check the online reputation of a website to better detect potentially malicious and scam websites. It fetches the SPF record from the DNS of the domain you want to check and. Domain owners can avoid SPF validation errors by taking a few simple measures given below: Use valid sender. net is a free online tool that lets you quickly and easily perform a DNS lookup to check DNS propagation and see information of any domain from DNS servers located in many countries all around the world. This API lets you check and validate the SPF record of any domain name, view a list of authorized IPv4 and IPv6 addresses published by the SPF record, view a list of "include" and "redirect" domain names extracted during the SPF records analysis, check if an IP address is authorized to send emails on behalf of the domain. com ~all. 3. Check for "use Secured Connection" if the SMTP server needs a secure connection (SSL, TSL). Next let's set up SPF. The syntax of an SPF record seems to be lexer-hostile and a lexer needs context to determine a token type or sometimes even boundaries. mimecast. Port25. BIMI implementation is quite straightforward, but it has a crucial prerequisite – ensure your DMARC policy is set to enforcement mode (p=quarantine or p=reject). The SPF alignment. Check if your domain has these 2 email signatures set up and valid. Send up to 10,000 notifications every month, for free. 2. Why you need DMARC, SPF and DKIM. An SPF record checker looks up the record for a queried domain, displays any records found and tests the record to find any issues that could create problems for mail delivery. MxToolbox Experts have created the best solution for setting up and monitoring your email delivery posture using DMARC, DKIM and SPF. Start MX Lookup. TXT Value: v=spf1 include:spf. Hackers use domains without SPF configuration. 2. You can simply enter email headers into the text box and then click on Analyze the Header Above. DKIM email authentication's goal is to prove the contents of the mail haven't been tampered with. SPF If you send the email using your own domain, be sure to create a valid SPF record to increase deliverability. port25. But, some legitimate services might make changes to the. About the SuperTool! All of your MX record, DNS, blacklist and SMTP diagnostics in one integrated tool. Validate your SPF record by using one of these SPF validation tools. Checking SPF Record Syntax: For this checking, the user needs to enter the domain name and the content of the SPF record. It will quickly test each port and display the results. From the IP, you can individually check each IP in anti-spam databases using an IP blacklist checker. We check for common errors such as using more than the 10 allowed DNS lookups. Manual mode is used for debug. SPF Syntax Validator. DMARC Record Checker is a free online DMARC diagnostic tool that allows you to verify and validate your domain's DMARC record. DNSSEC Validator Extension for Google Chrome. Generate the key pair, create your single Signing Profile in the Domain Keys section of Mail Policies, and click the “Generate” option under “DNS Text Record” once your profile is ready. a. Dedicated Support. All tools. Open main menu. Some more here you may try out. Enter the domain/host address in the space provided for that purpose and click the "DMARC Lookup" button. Google Admin Toolbox Check MX. Begin your DKIM and DMARC journey by first checking your DKIM record. Automated SPF flattening for one domain. Enter your SPF policy details (not the one shown in the example below) and use an address in your. It also features a DNS. The lookup limit. The SPF record syntax comprises several elements–Directives, Qualifiers, and Mechanisms. Repair. Value. Test your connection to any SMTP service. outlook. The SPF record checker, aka SPF record validator/tester, checks if an SPF record is published on a domain, and if the SPF record's syntax is correct. The Sender Policy Framework (SPF) is an email authentication protocol designed to prevent email spoofing, a common technique used in phishing attacks and email spam. tw does not have SPF but using Kitterman show that that domain has more than one entry! * the same occurs to pap. Hi, can some one tell what is the difference between these websites? Using MS show that the domain sinon. See full list on dnschecker. EasyDMARC’s SPF Record Validator tool allows you to check whether your SPF record is valid or not before publishing it in your DNS to avoid any typos and/or misconfiguration. br domain. An SPF Validator performs various tests on a domain. Summary + –Checking for the existence of SPF records. Mail Server Test Tool is a free online tool to validate the configuration of mail servers. Maintaining and accessing engineering data throughout a plant's lifecycle is challenging, but SPF provides a proven, custom solution for plant information management. Step 3: Copy the CNAMES shown in the pop up window. SPF Validator. fo: Forensic reporting options. Hi, can some one tell what is the difference between these websites? Using MS show that the domain sinon. This tool can help you generate a SPF Record or modify your current SPF Record as well as to check the modified record has the correct syntax. IP/Domain blacklists contain addresses identified as spam, malware, or other malicious activity sources. It also features a DNS lookup counter. It helps you debug DNS resolution issues, and to find the time it will take before your DNS records will propagate. Instant propagation check. The SPF Record Check is a diagnostic tool that acts as a Sender Policy Framework (SPF) record lookup and SPF validator. Scroll down to "Test an SPF record. Use this tool to lookup and verify a DKIM DNS TXT record and determine its public key length to detect the use of weak cryptographic DKIM keys (less than 1024 bits). In the Selected domain menu, select the domain you want to check. com -all. It was designed as a resource for understanding and troubleshooting deployment of the DNS Security Extensions (DNSSEC). After analyzing your subscriber list, it will estimate how many emails might bounce if you were to send content to everyone on your list. com: BIMI, DKIM, DMARC, SPF record checkers. After analyzing your subscriber list, it will estimate how many emails might bounce if you were to send content to everyone on your list. Allowed values are "0," "1," "d," and "s. Click on Settings > Domains. Known recipient, LDAP, or SMTP call forwarding recipient validation checks have yet to return a valid internal user. The Domain Owner wishes to have email that fails the DMARC mechanism check be treated by Mail Receivers as suspicious. com -all This record allows any host with an IP address specified in. email-validator: Validate Email Addresses. 1. Having more than one TXT record, starting with “ v=spf1 ” will cause unpredicted results of lookup by receiving mail server and SPF validation may fail. Note that automatic/dynamic SPF record flattening keeps the best of both worlds: the flattened SPF record still contain the IP addresses in the original SPF tree, while keeping a DNS lookup count. [1] [2] This authentication only applies to the email sender listed in the "envelope from" field during the initial SMTP connection. If there is no SPF record, it reports with. If you search online you will find numerous tools that supposedly optimise your SPF records by flattening all include, a and mx terms into a single, large SPF record consisting only of ip4 and ip6 terms. The SPF Record Check is a diagnostic tool that acts as a Sender Policy Framework (SPF) record lookup and SPF validator. Performing DNS queries costs the validator resources (bandwidth, time, CPU, memory). This is not how SPF works. Watch our video explanation to discover. Welcome to MxToolbox’s SPF record generator. Check MX is an easy to use DNS validation tool that looks for common MX record misconfigurations. Check the DNS propagation for any website using this online tool. allow_smtputf8 - the default value is True, if set to False the validate_email() won't validate internationalized. Website IPv6 accessibility validator: This site will check a URL and see what IPv6 tests it passes. com -all; TTL: 3600 (or your provider default) Save the record. Become a Partner. Domain owners using Google Workspace for their email might use a record that looks something like this: v=spf1. rf: afrf: The reporting format for forensic reports. Perform the following steps. Write the name of the domain as the Host. The percentage tag tells receivers to only apply policy against email that fails the DMARC check x amount of the time. Google Workspace domains typically use “ google ”. outlook. SPF is one of those things (just like the rest of email) that is easy on the surface, but can grow very complex quite quickly. To see results, simply send an email to: 86ecf83c@emailtest. SPF, DKIM and DMARC validation as well as email header analyzer. The SMTP tester will send the test mail to that address. This helps you to block fraudulent activity and also reduce. outlook. Check for "use authentication" if the SMTP server needs this. DKIM (DomainKeys Identified Mail) is an email authentication technique that allows the receiver to check that an email was indeed sent and authorized by the owner of the sending domain. Deliverability. ABOUT SPF RECORD CHECK. Test your connection to Sendgrid, Mailgun, Amazon SES, or any SMTP server. The SPF Record Lookup and Check is a diagnostic tool that acts as a Sender Policy Framework (SPF) record lookup and SPF validator. Check the SPF record using EasyDMARC's SPF Checker or command-line tool to ensure all the authorized IP addresses and sources are listed. Option 1. DKIM, SPF, DMARC DNS Verification Tool. Build your first notification in minutes. 6. · On Fri, 19 Apr 2013 16:10:49 +0000,. Simply send an email from any address from the domain in question and click the dropdown under the sender’s name. com: BIMI, DKIM, DMARC, and SPF record lookup. Mailgun’s email validation tool identifies invalid email addresses in your mailing list. No data. If you need help getting copies of your email headers, just read this tutorial. DNS Lookup for IP address. Visualizing the communication between email servers will help you understand what SPF, DKIM, and DMARC do and how these mechanisms work. No SPF Record for this domain. Click your profile icon and choose Account. Enter Email or Domain. Authenticate your IP addresses with SPF SPF stands for Sender Policy Framework and compares the email sender’s actual IP address to a list of IP addresses authorized to send mail from that domain. TXT. SPF is one of the oldest and one of the most reliable authentication tools (An SPF record can also be tested using an SPF Validator, which automatically tests it for anomalies). Note that if you check the newly published SPF record, it might take up to 1 hour before it appears in whatever tool you use to check it, due to DNS propagation. The defined flags are as follows: “y” – this domain is testing DKIM (test mode) “s” – verifiers MUST check for domain alignment (strict mode) Utilize dmarcian's DKIM Inspector to see if the public part of your DKIM signature has been implemented correctly in the DNS of your domain. The tools were easy to use and helped me build the SPF, DKIM and DMARC records to. The DNS records include but are not limited to A, AAAA, CNAME, MX, NS, PTR, SRV, SOA, TXT, CAA, DS, and DNSKEY. SPF Record Lookup: This checks to ensure. It fetches the SPF record from the DNS of the domain you want to check and subsequently parses the contents of the SPF record to understand the rules and mechanisms defined within it. Check SPF record with Kitterman. An SPF record starts with a “v,” indicating the SPF version used. Click on “Check” to run our online port checker. Simply put, the SPF specification tries to protect receiving email servers from SPF records that would otherwise force the receiving server to consume too many resources while. dmarcian’s gives organizations of all sizes control over how their email domains are being used with our DMARC Management Platform, which converts raw DMARC data into a clear picture of DMARC compliance, actionable steps, and infrastructure to improve and support the management of SPF and DKIM. Simply enter your domain name and scan it. 4 ip4:5. port25. To sum up, SPF validation works the same with a Safe SPF record as it does with a "vanilla" SPF record. SPF Validator API. SPFレコードが正しく登録出来ているか確認したいのですが、方法を教えてください。. SPF specification has a limit on the number of DNS lookups (10) required to fully resolve an SPF record. 0. · On Fri, 19 Apr 2013 16:10:49 +0000,. If you want to learn more about SPF, see our SPF knowledge base article. The first check an SPF validator performs is verifying if an SPF record is present. Domain owners can avoid SPF validation errors by taking a few simple measures given below: Use valid sender. example. SPF Policy Tester DMARC Tools Test your DMARC policy before deployment using our DMARC Policy Validator tool and make sure it will work as planned. protection. com provides another tool to test whether your SPF record is working. ABOUT EMAIL HEADERS. Boost your open rates, click-throughs, and delivery rates. br domain. Our SPF check tool will evaluate whether you have an existing SPF record published on your DNS. Note that automatic/dynamic SPF record flattening keeps the best of both worlds: the flattened SPF record still contain the IP addresses in the original SPF tree, while keeping a DNS lookup. Proofpoint: BIMI, DMARC, and SPF Record Check (select record type from navigation bar) ValiMail: DMARC and SPF Record. 3600 is the TTL (time to live) of the record in. SPF record generator to help with email delivery problems. Investigate Tool is powered by Red Sift's Digital Resilience Platform, which offers a range of products to protect your email, domains, and network. Authenticating a domain for Mailchimp means you, as the domain owner/administrator, authorize Mailchimp to send emails on behalf of that particular domain. Open your Outlook Express account. To. This test will list CNAME records for a domain in priority order. When recipients receive your emails, their spam filters automatically poke your domain to see if those signatures are not forged.