I am a very happy user of the free version of emClient 7.2 . I have a suggestion which hopefully you may consider for a future release.
When putting in a name to send mail to, in the composing mail process, you helpfully pick up on a part name with suggestions, so one can click on one of them to speed up the process. However, this comes with a downside, for which my suggestion would help obviate. It is picking up on addresses not just from the address book, but from previous email activity also, and for users like me who have a long history of emails for which 99% are obsolete and 1% valuable, the effort of weeding out the 99% is just not worthwhile. The problem is that people change their email addresses from time to time, so even if one has the latest address in the address book, the old ones will show up also, so there is a risk of going for one of the old ones rather than the current one.
My suggestion is that those addresses that have been detected in the address book have a distinct icon alongside them, the other ones not so, meaning it would be much easier to avoid sending to an old address that the recipient never sees. I find that dead addresses don’t always come back with undeliverable, only sometimes, and I have indeed fallen victim to this loophole.
I hope you find this helpful.