# Mostly clueless

but curious to find out
Jan 28, 2012

# Exim4 Fix Wrongly Decoded Mail Subject

If you are using Exim to transfer mails generated by internal software you probably often get mails with a really weird looking subject that starts with something like this:

    =?utf-8?Q?=5BPersonalverwaltung_=2D_Fehler_=23=31=37=38=5D_...

This problem arises when some system sends an email with more than 76 characters in the subject line (usually people don't do that).

> While there is no limit to the length of a multiple-line header field, each line of a header field that contains one or more encoded-word's is limited to 76 characters.

> The length restrictions are included both to ease interoperability through internetwork mail gateways, and to impose a limit on the amount of lookahead a header parser must employ (while looking for a final ?= delimiter) before it can decide whether a token is an "encoded-word" or something else.

> Excerpt from RFC2047

## Fix It

You can remove the length checking by adding the following to the main section of your `/etc/exim4/exim4.conf`. The main section usually ends with the first `begin` in that file.

    check_rfc2047_length = false

For further reference I recommend the official Exim documentation