- Plesk Onyx for Linux
- Webmail type of the main domain of a subscription is set to one value, for example to Horde.
- For additional domain under the subscription, webmail type is different, for example 'None'.
- After securing main domain with Let's Encrypt, webmail on additional domain is set to the same value as on the mail domain (Horde).
- The same issue might occur during automatic renewal of the certificates.
Let's Encrypt extension bug #EXTLETSENC-603 that is planned to be fixed in future extension updates.
Until a fix is available, use the same webmail type on all domains under subscription that are using Let's Encrypt.