Hi Evgeniy,
On 2019-04-16 09:20, Evgeniy Berdnikov via Exim-users wrote:
Hi, Konstantin.
On Tue, Apr 16, 2019 at 03:27:57AM +0000, Konstantin Boyandin (lists)
via Exim-users wrote:
One of users complained at having their message rejected by our mail
server (Exim 4.91), providing the below server response:
"Mail delivery error. This email issue occurs because your email
header
was rejected by recipient server.
The cause of rejection is because email reference header is more than
998 character. The 998 character limit is due to limitations in many
implementations that send, receive, or store IMF messages which simply
cannot handle more than 998 characters on a line. Receiving
implementations would do well to handle an arbitrarily large number of
characters in a line for robustness sake."
Probably config of your Exim contains in acl_check_data something
like:
deny
condition = ${if > {$max_received_linelength}{998}}
message = Mail delivery error. This email issue occurs because...
...
If you turn it off, your Exim could receive improperly formatted mail.
Indeed ti is. However, I think it's a bad idea to accept incorrectly
formatted mail, there will be cascade of further problems
The user's emails contain:
X-Mailer: Microsoft Outlook 15.0
Is there any Exim setting capable of re-formatting long headers
(i.e., split them into several lines, each below 998 character
limit) etc such headers, but allowing the incoming mail nonetheless?
Exim has no such built-in capability (AFAIK).
As for MS Outlook, it has bugs with mail formatting from version 10.
At most cases the "References:" header is broken and contain garbage.
There is no sense to reformat it, because this garbage reflects only
memory corruption and has no valid message-ids. You have better to
remove
References: header completely. Put in your config something like this:
acl_check_data:
...
warn
set acl_m_ref_len = ${strlen:$h_references:}
condition = ${if > {$acl_m_ref_len}{998}}
logwrite = References header has length=$acl_m_ref_len, removed
remove_header = references
Yes, I applied the above check/removal of extremely long References:,
that's definitely is the lesser evil.
We have quite long "threads" in local mail archives, with really
many References: entries, but still not exceeding 998 characters per
line.
Mail client is responsible for keeping References: withing reasonable
number of entries and below line length limit.
During many a years (12+) that was the case. We have just recently
stumbled upon a recipient whose mail system doesn't behave well.
Thanks to everyone having responded, for ideas and explanations.
Sincerely,
Konstantin
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