Skype for Slack - Move your slack discussions to a group skype call
MigrationWiz - MigrationWiz provides on-demand mailbox migration services through a fully automated cloud-based...
Calls on Slack - Make voice calls in Slack
MailStore - MailStore Home - A 100% free single-private-user desktop solution
Pingly - Your communication hub — Email, text & voice in one app
imapsync - Console-based utility for migrating IMAP mailboxes.