mailutils-imap4d 1:2.99.99-1ubuntu2 (arm64 binary) in ubuntu xenial

 GNU Mailutils is a rich and powerful protocol-independent mail framework.
 It contains a series of useful mail libraries, clients, and servers.
 .
 The GNU mailutils IMAP4 daemon implements the Internet Message Access
 Protocol, version 4rev1 as per RFC 2060. It supports the "Namespace"
 capability and GSSAPI authentication mechanism. It is able to get the
 authentication information from the system user database as well as from
 a SQL database of arbitrary structure. The PAM framework can also be
 used for authentication purposes. Additionally, mailutils imap4d supports
 virtual mail domains and has TLS support via GNUtls. GNU mailutils supports
 the mbox, MH and Maildir mailbox formats.