I’m a new user, I just paid for their products online yesterday, But I didn’t get their activation email, I’ve already sent an email, but there’s still no reply,.Is there anyone of them in charge of these problems?
I found their web page, which is basically difficult to contact him, Even if i can get in touch, I can only use email, It’s very inefficient, Can you provide more effective communication channels?
This is a user supported forum, so it is only fellow users here. 
If you want to contact eM Client, their contact email addresses are on the website. Just be aware that they don’t work on the weekends, so you will need to wait till Monday for a reply.
Otherwise, check the spam folder for the activation email. If it is not there, you can have it resent by entering the email address you used to register in the Lost Activation Key page.