Where will temporary errors manifest from Yahoo and Google's new email authentication policies?
Summary
What email marketers say6Marketer opinions
Email marketer from Reddit explains that temporary errors will be visible in the Delivery Status Notifications (DSN) also known as bounce messages. They will contain 4xx SMTP codes
Email marketer from Email Geeks explains that temporary errors will show up in GPT as Delivery Error data along with the reason for the temp error.
Email marketer from EmailToolTester suggests temporary errors could present as soft bounces within email marketing platforms. These platforms will categorize messages that receive temporary failure responses as soft bounces and will usually attempt to resend these.
Email marketer from Email Geeks shares information from Google indicating that a 5.7.26 error will occur, including example text.
Email marketer from Stack Overflow indicates that temporary errors may delay email delivery, with affected messages remaining in the sending server's queue for a certain period before being retried or ultimately bounced as a hard failure if the issue persists.
Email marketer from EmailOnAcid shares that temporary errors may lead to delayed delivery and/or soft bounces, but additionally the error codes will appear in delivery reports.
What the experts say2Expert opinions
Expert from Word to the Wise explains that temporary errors may appear as greylisting responses, where the receiving server temporarily rejects the email to combat spam and requires the sending server to retry later, which will manifest in mail logs.
Expert from Spamresource explains that temporary failures will often appear as deferrals of email either with an SMTP code starting in 4 or temporarily blocked with a message similar to “throttled due to detected spam activity”. These are usually accompanied by a retry time at which point the system believes it will be able to accept the message.
What the documentation says3Technical articles
Documentation from Yahoo Help Central shares that temporary failures may lead to 421 SMTP response codes. These are usually associated with temporary server issues, rate limiting, or greylisting, requiring the sender to retry delivery.
Documentation from RFC 5321 defines SMTP reply codes where 4xx is a temporary failure and 5xx is permanent. If the user does nothing then the mailer will retry. Specific error examples aren't provided in RFC it provides a framework.
Documentation from Google Workspace Updates explains that temporary errors related to authentication issues may manifest as 4xx series SMTP error codes. These indicate transient problems, like temporary DNS issues or greylisting, and suggest the sending server retry delivery later.