CNAME for imap, smtp and zsync

CNAME for imap, smtp and zsync

Hi all
As described in this topic i have added CNAME records for

- imap.zoho.com
- smtp.zoho.com
- zsync.zoho.com

But it makes problems using my own url, for example imap.mydomain.com.
In thunderbird it tells me that Certificate is not valid and Exchange Account for iphone
can not be created using zsync.zoho.com. Server verification error.

How to do to use my own domain for Emailserver Setup?

Thank you

BR, Walter