squirrelmail-sent-confirmation 1.6-2 (s390x binary) in ubuntu yakkety

 This plugin displays a confirmation message above the message index after a
 message is successfully sent. It can also display a screen offering the option
 to add any of the message's recipients to the user's address book or move,
 delete or return to the original message in the case of replies and forwards.
 .
 SquirrelMail is a standards-based webmail package written in PHP. It runs on
 top of any IMAP server.