How it plugs in
—Public API
NoOpen source
YesFree tier
Signal on Mail Server Software4.8#32 of 34

Pricing
- Open editionOpen-source license · MTA, secured front end, or mass email sender · SMTP and MIME filteringOn request
As viridit.com lists them, checked 23 Sept 2026.
Near it
All alternatives →- HDHCL Domino#31 on this board
- OXOpen-Xchange App Suite#33 on this board
- CPCommuniGate Pro#30 on this board
- PPowerMTA#34 on this board
- ZSZentyal Server#29 on this board
- MMMDaemon Messaging Server#28 on this board
- KCKerio Connect#27 on this board
- MEMicrosoft Exchange Online#26 on this board
- HHaraka#25 on this board
- DDovecot#24 on this board