[Dovecot] Temporary files

[Timo Sirainen]

In v1.0 .. v1.1 deliver was writing incoming >128k mail to /tmp file (to
avoid reading it all into memory). In v1.2 I moved it to user's home
directory. This slowed deliveries for NFS users. Also people with
filesystem quota had trouble since now user required twice as much
available quota to save a message. The FS quota problem was "solved" by
having quota-fs plugin change the default temp file path to /tmp.

So why was the move made in the first place? Because a) some people had
small (maybe ramfs) /tmp and Dovecot was eating it all up and b) to
avoid any potential security issues with storing per-user files to a
shared directory.

I'm now thinking about a new setting (mail_temp_dir?) for v2.0 where
these temp files would be stored (lda, lmtp, some others in future).
Maybe the b) problem isn't that huge, so maybe there doesn't need to be
a way to store them to user's home. So that leaves a) problem. Maybe the
setting could default to /var/tmp instead of /tmp? That probably has
more disk space available usually. (I hope /var/tmp is available
everywhere?)

Any thoughts?