Anyone ever run into an issue where a customer's webmail.<domain>.com will return their home page instead of the webmail login screen? Traditionally, we'd fix it via /usr/local/psa/admin/bin/httpdmng --reconfigure-domain <domain> and things would work, until someone else on the same server reports the same thing, repeat. This has been going on since at least Plesk 11.5 but possibly older.
I ultimately found the issue is that the /etc/httpd/conf/plesk.conf.d/webmails/horde/<domain>_webmail.conf files were disappearing at random. We've put a script in place to compare the contents of the directory against the psa.domains table on domains where email is enabled, but there must be some bug that is causing this to occur. The only factor that seems to play a role in this is that the problem only occurs on servers where there's at least 150 domains. We've never had this occur on any server with a smaller amount of domains present.
I ultimately found the issue is that the /etc/httpd/conf/plesk.conf.d/webmails/horde/<domain>_webmail.conf files were disappearing at random. We've put a script in place to compare the contents of the directory against the psa.domains table on domains where email is enabled, but there must be some bug that is causing this to occur. The only factor that seems to play a role in this is that the problem only occurs on servers where there's at least 150 domains. We've never had this occur on any server with a smaller amount of domains present.