How I can remove the mail client from Elementary OS Loki 0.4 through command line? I don't need it but can't uninstall it in the Application Center as it freezes.
AppCenter is still in development so it can be buggy. In Terminal, use:
sudo apt purge pantheon-mail
Just use included App Center, in updates tab, find "Mail", choose "Uninstall" and enter password. After that mail will be removed from Your PC