Support Truncating Lines Longer than 1000 Charachters

[Matt Corallo]

Some MUAs violate the SMTP RFC and send mail with lines longer than 1000 characters [1]. In the case of postfix, these lines are forwarded as-is to the milter[2], only truncated later by inserting <CR><LF><SPACE>[3]. This causes DKIM failures as the signing occurs before the mail is changed. It would be nice if there would be an option to expect such changes ala FixCRLF.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1731007
[2] https://marc.info/?l=postfix-users&m=163176643901328&w=2
[3] http://www.postfix.org/postconf.5.html#smtp_line_length_limit

[Scott Kitterman (kitterman)]

I think this is reasonable, but it would be a significant change since we would have to fold the lines and replace the message body, not just insert a new header field like we do now.