I have another suggestion, eM client notifications are really good. but if i sent a mail sometimes i have to check it in sent items whether to know it sent or not… so if you can make notifications for sent mail. it’ll be very useful. and i like read receipt concept so much 
thanks
Hi, notifications for sent email is currently not a planned feature for eM Client, you can use read/delivery receipts to confirm your mail was successfully sent or use the Outbox smart folder.
Outbox displays a number of unsent messages, so if you send a message it should first appear there and eventually disappears and is moved to your sent folder after the message is sent.
Or you can use the “operations” window to see if there’s any activity on your accounts (such as sending).
Hope this helps,
Paul.