- Plesk for Windows
On Let's Encrypt issuing in Domains > example.com > Let's Encrypt checkbox for Secure webmail on this domain is disabled with the following notice:
PLESK_INFO: Securing "mewebmail" webmail service is not supported. Configure mail settings.
MailEnable Webmail is used as a Webmail for the domain in Domains > example.com > Mail Settings > Webmail ;
Securing MailEnable Webmail with Let's Encrypt is not yet supported.
This is feature request with ID #EXTLETSENC-134, which will be implemented in one of the future Plesk updates.
Consider following the article to be notified when the feature will be implemented - the article will be updated.
As a workaround, Horde Webmail can be used instead. Switch webmail using the article How to change webmail for a subscription?