11.11.22, 13:02 +0100, Juan Smitt Jr:
Can you help me please understand the "message-id" header?
Sometimes it's missing from the emails and i.e. gmail rejects these emails.
Is it added by the email client (application) or is it added by postfix?
The Message-ID header contains an unique identifier for the particular
message[1]. Every message should have one, and in general, especially
when real people communicate via e-mail, it's the sending MUA's (mail
client's) job to create one.
Depending on situation (for example when postfix itself creates a status
message) and configuration postfix might create a Message-ID, though.
[1]: <https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.4>
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Regards
mks
