Description: Known bugs and to-do items in fetchmail
Keywords: fetchmail, POP3, IMAP, bugs

# Fetchmail Bugs and To-Do Items

Note that there is a separate TODO.txt document of different content than this.

I try to respond to urgent bug reports in a timely way. But fetchmail is now pretty mature and I have many other projects, so I don't personally chase obscure or marginal problems. Help with any of these will be cheerfully accepted.

## Serious

Let IMAP code use UID and UIDVALIDITY rather than relying on flags that everyone can alter.

## Normal

POP3 hang when polling mail with NUL char that is rejected (David Greaves) https://lists.berlios.de/pipermail/fetchmail-devel/2004-October/000154.html

It has been reported that multidrop name matching fails when the name to be matched contains a Latin-1 umlaut. Dollars to doughnuts this is some kind of character sign-extension problem. Trouble is, it's very likely in the BIND libraries. Someone should go in with a debugger and check this.

The Debian bug-tracking page for fetchmail lists other bug reports.

## Cosmetic

Alan Munday suggests message change MULTIDROP without ENVELOPE:

    fetchmail: warning: MULTIDROP configuration for pop.example.org requires the envelope option to be set!
    fetchmail: warning: Check ENVELOPE option if fetchmail sends all mail to postmaster!

## Feature requests/Wishlist items

Feature request from "Ralf G. R. Bergs" <rabe@RWTH-Aachen.DE> "When fetchmail downloads mail and Exim+SpamAssassin detecs an incoming message as spam, fetchmail tries to bounce it. Unfortunately it uses an incorrect hostname as part of the sender address (I've an internal LAN with private hostnames, plus an official IP address and hostname, and fetchmail picks the internal name of my host.) So I'd like to have a config statement that allows me to explicitly set a senderaddress for bounce messages."

In the SSL support, add authentication of Certifying Authority (Is this a Certifying Authority we recognize?).

Laszlo Vecsey writes: "I believe qmail uses a technique of writing temporary files to nfs, and then moving them into place to ensure that they're written. Actually a hardlink is made to the temporary file and the destination name in a new directory, then the first one is unlinked. Maybe a combination of this will help with the fetchmail lock file."

Maybe refuse multidrop configuration unless "envelope" is _explicitly_ configured (and tell the user he needs to configure the envelope option) and change the envelope default to nil. This would prevent a significant class of shoot-self-in-foot problems.

Given the above change, perhaps treat a delivery as "temporarily failed" (leaving the message on the server, not putting it into .fetchids) when the header listed in the "envelope" option is not found. (This is so you don't lose mail if you configure the wrong envelope header.)

Matthias Andree writes:

> NOTE that the current code need optimization, if I have unseen articles 3 and 47, fetchmail will happily request LIST for articles 3...47 rather than just 3 and 47. In cases where the message numbers are far apart, this involves considerable overhead - which could be alleviated by pipelining the list commands, which needs either asynchronous reading while sending the commands, or knowing the send buffer, to avoid deadlocks. Unfortunately, I don't have the time to delve deeper into the code and look around.

> Note that such a pipelining function would be of universal use, so it should not be in pop3.c or something. I'd think the best approach is to call a "sender" function with the command and a callback, and the sender will call the receiver when the send buffer is full and call the callback function for each reply received.

> See the ESMTP PIPELINING RFC for details on the deadlock avoidance requirements.