WebMail issue with 2 IPs

Hi. I have 2 email domains for my server. Server has 2 ips, one is external, to reach from internet. Another ip is internal, to make data exchange inside local network. One domain email work properly, i can reach webmail and receive letsencrypt ssl. But another email address suddenly has internal ip in configs. When i try to change it manually to external ip, i can reach webmail. But when I try to get SSL for email domain, all settings reset back, I have again internal IP for email domain and of course I cant get ssl certificate for it.

Any Suggestion???

What does DNS look like for that domain?

Add a web domain for domain.com and assigned it the public ip

Other option is to disable the internal by changing it to “dedicated” instead of shared and assign it to the admin user…

Long time ago I set test[dot]domain[dot]com as web and domain.com as email domain. domain[dot]com as web was on another server. But when I set for test[dot]domain[dot]com alias domain.com and www[dot]domain[dot]com, settings for email domain[dot]com changed to internal IP suddenly (why???). I solve problem by removing domain[dot]com as alias and set it as real web domain. Thanks.