Hello,
i want use em client but how can i makes sure its safer than gmail and also they do not read my emails ?
Thank you.
If THEY (who? Google?) wants to read your emails - they find a way, even if you’re using POP3.
If you’re talking about eM Client crew, then it’s a little paranoid. 
Hahaha what a question!
eM Client is for those who want to work with their emails and contacts etc offline + online. so if you have security issues. please do not use it, because in that case no one can satisfy you. other than that, you can trust em client and stay happy with your offline works.
eM is the best.
eM Client does not store your data on their servers. It is stored on your providers servers (for example, Gmail). Your connection is direct to your provider, not via eM Client servers. Worry about Google, not eM Client.