Symptoms
You are unable to send emails, and you find a message similar to one of the following in the Exim mainlog.
2022-03-22 08:53:12 1nWfsm-0004op-5k ** user@domain.tld R=dkim_lookuphost T=dkim_remote_smtp: message has lines too long for transport
2022-11-10 13:20:45 1ot2nl-0002E5-U2 ** user@domain.tld R=dkim_lookuphost T=dkim_remote_smtp H=mail.domain.tld [203.0.113.2] X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no: SMTP error from remote mail server after end of data: 500 Line too long
Description
Some email clients ignore RFC 5322 and send emails with lines exceeding the 998-character limit. Modifying the message_linelength_limit
value allows Exim to accept messages exceeding the 998-character limit.
Workaround
- Log into WHM as the ‘root’ user.
- Navigate to "Home / Service Configuration / Exim Configuration Manager."
- Click the "Mail" tab.
- Scroll down to the "Maximum line length for SMTP transports" option.
- Select the "Maximum line length for SMTP transports" textbox.
- Enter the desired value in the textbox.
- Click the "Save" button.