Hi,

I've run into an issue with Exim 4.80 (Debian Stable amd64) where sometimes the sender envelope address (the address given after the MAIL FROM: command) is truncated to a random number of characters. It usually happens with addresses containing equals signs (=), pluses (+) or hyphens/dashes (-).

For example:

s-vbh-bxwddjs2uvl2kehv-cjlo30lt6uimlo8jyswye5isz2vgi5...@bounce.linkedin.com
s-vBH-bxWddjS2uVL2kEHv-cjlO30LT6UimlO8JyS

Or Facebook:

[email protected]
notification+zrdp

Exim registers these emails with their truncated sender address in the mainlog:

2014-06-10 09:34:57 1WuGa7-0007ik-VS <= notification+zrdp H=outmail023.ash2.facebook.com (mx-out.facebook.com) [66.220.155.157] P=esmtps X=TLS1.0:DHE_RSA_AES_128_CBC_SHA1:128 S=8683 [email protected]

However, our custom logging in acl_smtp_mail registers the entire address when we log $sender_address. Somewhere in the process, the address gets truncated.

Because our mail server is functionally a spam proxy, it sends all valid emails to a smarthost. Exim then uses the sender address for the MAIL FROM: command. Because the address is truncated, it tries to qualify it with its own hostname causing invalid addresses like:

[email protected]
[email protected]

This of course fails, because our server doesn't accept these invalid addresses during verification phase of the smarthost. The icing on the cake: if I enable debugging in acl_smtp_mail, the problem goes away!

warn
condition = ${if match {$sender_address}{\N(bounce|mailer|notification|alert)\N}}
  control = debug/tag=.$sender_host_address/opts=+all

This is the only difference in the entire ACL for these sender addresses. It makes the problem virtually impossible for me to debug. My guess would be a timing issue of sorts.

Does anyone have any idea what could cause this?

--
Jelle Raaijmakers


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