bounce verification

[DISmekalin]

Error reports began to come more recently like:

#5.0.0 smtp; 5.1.0 - Unknown address error 550-'Callback setup failed while verifying <address@domain.zone>\n(result of an earlier callout reused).\nThe initial connection, or a HELO or MAIL FROM:<> command was\nrejected. Refusing MAIL FROM:<> does not help fight spam, disregards\nRFC requirements, and stops you from receiving standard bounce\nmessages. This host does not accept mail from domains whose servers\nrefuse bounces.\nSender verify failed' (delivery attempts: 0)> #SMTP#

Tell me, please, what settings need to be adjusted for a particular domain or for all?

Thanks in advance.

[martin.eppler · Accepted solution]

This seems to be a classical constellation where you're using Bounce Verification while the destination domain is using SMTP Callback. As SMTP callback uses an empty envelop sender when attempting to verify if the sender email address exists, it collides with the Bounce Verification that expects a the bounce verification tag back.

The only way forward would be to either exclude the particular destination from bounce verification or to discuss with the destination that they either use a non-empty envelope sender address for SMTP callback or to not attempt SMTP callback for your domain.

[DISmekalin]

We have added a third-party domain in Sender Verification Exception Table and there is no NDR.

It took a letter and confirmation came.