A while back my Thunderbird email client started crashing. It mostly happened after I'd spent a long time composing an email and then bang, gone. A lot of time wasted re-composing the email.
Searched for and decided on eM Client as an alternative. Looked decent and I had no issues paying for a license. I trialed it for 6 months but eventually switched back to Thunderbird. Overall I liked eM Client but just couldn't get past the following:
1/ Slow startup. Those extra few seconds looking at the orange splash screen began to really annoy.
2/ Opening individual emails also seems to have unnecessary delay
3/ Custom "From" email addresses. Very easy to do with Thunderbird from the composition window, however with eM Client an alias first needs to be set up. Again, at first this doesn't seem too bothersome, but after a while...arghh!
4/ unread emails filter. click and it selects unread emails, but as soon as you read one of these emails it throws you back to where the email was in your inbox. This is very frustrating when trying to read all your unread emails as you have to keep clicking unread emails. Thunderbird's implementation is way superior.
On the flip-side it never crashed and the CardDAV support is superior (note Thunderbird beta finally has native support for this).
Anyway I'm back with Thunderbird. And it's crashed on me again. I think it's an issue saving drafts to remote email server, so I've switched to local folders for drafts which will hopefully resolve the issue.
