Exim is a mail transfer agent used on Unix-like operating systems. It is freely available under the GNU GPL and it aims to be a general and flexible mailer with extensive facilities for checking incoming e-mail.
We do not use Qmail.
Maildir is a widely-used format for storing e-mail that does not require application-level file locking to maintain message integrity as messages are added, moved and deleted. Each message is kept in a separate file with a unique name. All changes are made using atomic filesystem operations so that the filesystem handles file locking concurrency issues. A Maildir is a directory (often named Mail) with three subdirectories named tmp, new, and cur.
We do not use mbox.
- Missing folders after converting to maildir