Configuring postfix to use SendGrid SMTP relay with fixed FROM address but need to append REPLY-TO of original sender

kcfez

2/14/24, 3:52 PM

I have been trying to resolve for a couple of months using multiple different configurations.

The local delivery to a Dovecot mailbox ([email protected]) keeps the original sender ([email protected]) in the FROM address. The remote delivery using SendGrid SMTP server via a virtual forward to ([email protected]) works if:

in smtp_header_checks if there is

/^From:(.*)$/   REPLACE From: [email protected]

and in main.cf

sender_canonical_classes = envelope_sender
smtp_header_checks = regexp:/etc/postfix/smtp_header_checks

I have tried to add a reply-to to the header so that the receivers, who get the forwarded email, can reply to it.

In smtp_header_checks I put

/^From:(.*)$/  REPLACE Reply-To:$1<br>
/^From:(.*)$/   REPLACE From: [email protected]

but this gives a 550 Error

Feb 14 13:40:03 club-jowett-vm postfix/smtp[12857]: BB2AD65E91: replace: header From:  <[email protected]>: From: [email protected]  Reply-To: <[email protected]>
Feb 14 13:40:03 t-vm postfix/smtp[12857]: BB2AD65E91: to=<[email protected]>, orig_to=<[email protected]>, relay=smtp.sendgrid.net[54.228.39.88]:587, delay=2.3, delays=1.6/0.19/0.48/0.05, dsn=5.0.0, status=bounced (host smtp.sendgrid.net[54.228.39.88] said: 550 The from address does not match a verified Sender Identity. Mail cannot be sent until this error is resolved. Visit https://sendgrid.com/docs/for-developers/sending-email/sender-identity/ to see the Sender Identity requirements (in reply to end of DATA command))

I have tried other configurations one of which added the reply-to but some receivers rejected the email because of multiple ReplyTo headers.

I have also tried /^From:(.*)$/ PREPEND Reply-To:$1 which gives the same 550 error.

Has anyone a configuration that works, please?

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postfix

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danielj

7/31/24, 5:03 PM

Did you resolve this? I've been banging my head against the same problem for days. It seems like it would be a fairly common use case.

kcfez

8/1/24, 7:53 PM

Sadly no. I suspect the lack of a solution is there to block spoofing and spam. I live in hope.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Configuring postfix to use SendGrid SMTP relay with fixed FROM address but need to append REPLY-TO of original sender

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