Skype for Slack - Move your slack discussions to a group skype call
imapsync - Console-based utility for migrating IMAP mailboxes.
Calls on Slack - Make voice calls in Slack
iSync - iSync is a software application published by Apple Inc.
CallKite - Your website’s video call center in just one click.
OfflineIMAP - OfflineImap synchronizes email between an IMAP server and a MailDir or between two IMAP servers.