I created a subdomain for a Letsencrypt-mail test (mail.mydomain.com).
After the test, I deleted them again in EHCP.
At the next reboot Apache2 did not come up because:
AH00112: Warning: DocumentRoot [/var/www/vhosts/mydomain.com/mydomain.com/httpdocs/subdomains/mail] does not exist
AH00526: Syntax error on line 19 of /var/www/new/ehcp/apachehcp_subdomains.conf:
SSLCertificateFile: file '/etc/letsencrypt/live/mail.mydomain.com/fullchain.pem' does not exist or is empty
Action 'start' failed.
Then I created the path manually via FTP.
...httpdocs/subdomains/mail/logs
Apache2 then started.