How to create Let's Encrypt certificate for webmail if the website is hosted on another server without Plesk?

Question

How to create Let's Encrypt certificate for webmail if the website is hosted on another server without Plesk?

Main domain in Plesk has the hosting type Website.

Answer

1. Set Webmail to "None" in Domains > example.com > Mail > Mail settings
2. Create a subdomain webmail.example.com in Subscriptions > example.com > Add Subdomain.
3. Issue a Let's Encrypt certificate for it in Domains > webmail.example.com > Let's Encrypt.
4. Secure the webmail with this certificate in Domains > example.com > Mail > Mail Settings > SSL/TLS certificate for webmail.
5. Delete the subdomain webmail.example.com in Domains > webmail.example.com > Remove Subdomain.

Note: Such certificate will not be renewed automatically. Use the above steps for renewing such certificate when its expiration date is close.