Issue reproduction: 1. Create a new virtual server or sub-server with disabled mail feature (do not accept mails for this server), e.g. subdomain.domain.tld 2. SSL certification request fails 3. Go to "Server Configuration" > "SSL Certificate" > Select tab "Let's Encrypt" > see the default domains (a) subdomain.domain.tld, (b) www.subdomain.domain.tld and (c) mail.subdomain.domain.tld 4. When trying to manually request a new Let's Encrypt certificate it still fails 5. When enabling / disabling the "mail" feature for the virtual server it does not correct the SSL configuration for Let's Encrypt 6. Change the default domain requests to only (a) subdomain.domain.tld and (b) www.subdomain.domain.tld 7. Again, try to request the Let's Encrypt certificate --> Successful
10/10 times reproducible.