I've been running a FUDforum installation with maillist.php integration successfully for over 11 years (my thanks to FUD forum authors and maintainers!)
Currently using 3.0.6
Over the last few months I've noticed increasing problems of messages failing to be integrated into the forum and have tracked this down to messages which are encoded in base64 e.g. mail headers like
It seems that for a significant number of my subscribers their corporate Exchange mailserver is now enforcing encoding in this way i.e. users are unable to change their mail format for me.
And it also seems that maillist.php cannot handle this, presumably because the base64 encoded message has no plain-text part for it to use.
I've dug further and find that there is code to decode base64
And I've checked the source of some incoming messages and found that their base64 section is valid and can be decoded by the php base64_decode function which is what is used in scripts_common.inc
So this is more mysterious now!
FUDforum is equipped to decode and use base64 text, and my base64 section is decodeable by the php on my server.