My current server is few years old. And now runs plain Debian. Beginning I started using that server during my work at Canonical. So it got Ubuntu installed. According to OVH panel it was 13.04 release. Then 13.10, 14.04 and finally 16.04 landed.
Mutt website says: “All mail clients suck. This one sucks less.” Then Mutt-NG adds “Mutt sucks less – but it still sucks!”. And this is true. Thunderbird definitely sucks. But I still use it. I have three email accounts: private