On Ubuntu 18.04.5 with Webmin (1.973), Virtualmin (6.16.gpl), Usermin (1.823) latest versions upgraded in the last 12 hours we’ve begun hitting an error that we haven’t experienced previously.
Updating module virtual-server to version 6.16.gpl. Latest version of Virtualmin.
Apparently due to Usermin and the webmail module on port 20000 combined with the regular apache web-server redirect from http://webmail.domain.tld to http://domain.tld:20000 and consequently Let’s Encrypt not being able to access it, with:
Domain: webmail.domain.tld Type: connection Detail: Fetching https://domain.tld:20000/: Invalid port in redirect target. Only ports 80 and 443 are supported, not 20000