--- title: "Validating To: and From: Addresses | DuoCircle" description: "We are making two new changes to the way that the email system processes mail in an attempt to cut down on spam." image: "https://www.duocircle.com/images/og-default.png" canonical: "https://www.duocircle.com/blog/spam-filtering/validating-to-and-from-addresses/" --- Quick Answer DuoCircle now checks that the domains in the SMTP envelope are registered and have valid DNS records. If the sender or recipient domain does not resolve, the message is deferred. The change applies to both Outbound SMTP and Inbound Gateway customers; inbound domains can be whitelisted as needed. Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=Validating%20To%3A%20and%20From%3A%20Addresses&url=undefined%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F&title=Validating%20To%3A%20and%20From%3A%20Addresses "Share on Reddit") [ ](mailto:?subject=Validating%20To%3A%20and%20From%3A%20Addresses&body=Check out this article: undefined%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F "Share via Email") ![To and From](https://media.mailhop.org/duocircle/images/2018/09/SPF-record-checker-3654.jpg) We are making two new changes to the way that the email system processes mail in an attempt to cut down on spam. We are adding additional validations and checks to ensure that the domains mentioned in the SMTP envelope are valid and have a functional DNS record. These changes impact inbound and outbound customers differently, but the core change is the same. If the sender or the recipient of a message is not a registered domain name we will defer accepting the message. Outbound SMTP: Inbound Gateway: You will be able to whitelist inbound domains. ![Brad Slavin](https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg) Brad Slavin General Manager General Manager at DuoCircle. Product strategy and commercial lead across the email security portfolio. ## Secure your email infrastructure Protect, authenticate, and deliver. Contact our team to find the right solution. [Contact Sales](/contact/) [Explore Products](/products/) Share this article [ ](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.duocircle.com%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F) [ ](https://twitter.com/intent/tweet?text=Validating%20To%3A%20and%20From%3A%20Addresses&url=https%3A%2F%2Fwww.duocircle.com%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F) [ ](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.duocircle.com%2Fblog%2Fspam-filtering%2Fvalidating-to-and-from-addresses%2F) Copy Related Articles - [ ![Secure Email Gateway](https://media.mailhop.org/duocircle/images/2021/03/spf-record-9932.jpg) A Guide On Email Gateway: What It Is And The Importance Of A Secure Email Gateway Spam Filtering ](/blog/spam-filtering/a-guide-on-email-gateway-what-it-is-and-the-importance-of-a-secure-email-gateway/) - [ ![Anti-Spam Filters](https://media.mailhop.org/duocircle/images/2020/06/email-sending-services-7776.jpg) Anti-Spam Filters and How They Work Spam Filtering ](/blog/spam-filtering/anti-spam-filters-and-how-they-work/) - [ CERT Advisory Symantec and Norton Critical Vulnerability Spam Filtering ](/blog/spam-filtering/cert-advisory-symantec-norton-critical-vulnerability/) - [ ![Cloud-Based Spam Filtering Protects](https://media.mailhop.org/duocircle/images/2018/09/spf-permerror-7776.jpg) Cloud-Based Spam Filtering Protects Your Company Spam Filtering ](/blog/spam-filtering/cloud-based-spam-filtering-protects-your-company/) ## Related Articles [ Spam Filtering 5m A Guide On Email Gateway: What It Is And The Importance Of A Secure Email Gateway Mar 4, 2021 ](/blog/spam-filtering/a-guide-on-email-gateway-what-it-is-and-the-importance-of-a-secure-email-gateway/)[ Spam Filtering 5m Anti-Spam Filters and How They Work Jun 19, 2020 ](/blog/spam-filtering/anti-spam-filters-and-how-they-work/)[ Spam Filtering 1m CERT Advisory Symantec and Norton Critical Vulnerability Jul 6, 2016 ](/blog/spam-filtering/cert-advisory-symantec-norton-critical-vulnerability/)[ Spam Filtering 3m Cloud-Based Spam Filtering Protects Your Company Sep 10, 2018 ](/blog/spam-filtering/cloud-based-spam-filtering-protects-your-company/) ```json {"@context":"https://schema.org","@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com","logo":{"@type":"ImageObject","url":"https://www.duocircle.com/images/duocircle-logo.png"},"description":"DuoCircle is a portfolio of specialized email products covering protection, authentication, delivery, and routing. 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