Hello,
Sometimes, when delivering mails, this warning appears in my syslog:
> lda(...): Warning: Failed to parse return-path header: Invalid
character in localpart
dovecot-lda still exits with 0 and the mail is inserted into my inbox.
Looking at the mails in question, I determined that the error is caused
by a multiline Return-Path header. Here's a testcase:
--- snip ---
Return-Path:
<nowh...@example.com>
From: "Nowhere" <nowh...@example.com>
To: redac...@example.com
Subject: Testcase for lda warnings
Date: Wed, 31 Jan 2018 12:00:00 +0000
This is a message body.
--- snap ---
Copy into a file, with \r\n line endings, then run something like this:
> cat testcase.txt | /usr/lib/dovecot/dovecot-lda -e -d '<username>'
with a username recognized by your running dovecot installation.
The header is 'Return-Path:', \r\n, two spaces, '<...>', \r\n
According to rfc2822 folding rules, that should be valid - the
Return-Path header allows CFWS at that location.
The error message originates in lib-lda/mail-deliver.c in
mail_deliver_get_return_address(), while the invalid character message
seems to originate from one of several places in lib-lda/mail-deliver.c
Ciao,
Christian Authmann
