courier-imap-ssl 4.10.0-20120615-1ubuntu5 (arm64 binary) in ubuntu vivid

 The Courier mail transfer agent (MTA) is an integrated mail/groupware
 server based on open commodity protocols, such as ESMTP, IMAP, POP3, LDAP,
 SSL, and HTTP. Courier provides ESMTP, IMAP, POP3, webmail, and mailing list
 services within a single, consistent, framework.
 .
 IMAP over SSL is handled by the regular IMAP daemon from courier-imap
 in conjunction with the SSL/TLS wrapper supplied by courier-ssl.