OfflineIMAP

gomailsync   (Compare Project)

Mostly written in Go

License: GPL2

Dovecot   (Compare Project)

Mostly written in C

License: BSD-3-Clause, lgpl21, mit

Xfce Mailwatch Plugin   (Compare Project)

Mostly written in C

License: gpl

VMime   (Compare Project)

Mostly written in C++

License: gpl3, vmime-commercial-license

maildirman   (Compare Project)

License: gpl

KBiff   (Compare Project)

License: Unknown

notmuch   (Compare Project)

Mostly written in shell script

License: gpl3_or_later

maildirproc   (Compare Project)

Mostly written in Python

License: gpl

mairix   (Compare Project)

Mostly written in C

License: gpl

Simple Groupware   (Compare Project)

License: gpl