Question Secure mail protocols while website on other server (A to a different IP)

[easyware]

Server operating system version

CentOS Linux 7.9.2009 (Core)

Plesk version and microupdate number

lesk Obsidian v18.0.61_build1800240603.06

Hi, I have this issue with one of my customers.
I have always provided web hosting and mail services, the customer decided to develop the website with another company which wanted to use his own server for hosting.
I have changed the DNS settings so the A record points to this external server's IP.
The issue comes generating Let's Encrypt Certificate to secure the mail protocols and the webmail as the ACME Challenge obviously fails.
The website's company is strict about using his server for hosting, Is there a way I can solve the problem?

 

[Kaspar@Plesk]

Instead of using their domain name for connecting to the mail services on your server, your customer could connect using the host name of your server.

Issues Let's Encrypt Certificate for the mail protocol will fail, but should still be possible for webmail (if all other certificate options are not selected).