groat-smtpd

https://github.com/pzb/groat-smtpd

Groat SMTPD is a flexible extensible RFC-compliant implementation of the Simple Mail Transfer Protocol. It includes support for the 8bit-MIMEtransport, Authentication, BINARYMIME, CHUNKING, Pipelining, Message Size Declaraion, and STARTTLS service extensions. It also includes framework for the non-standard ONEX and VERB verbs and the SASL LOGIN mechanism.