How to provide a https webmail

[clivejo]

What is the best way to provide https connection for clients? I would like something like https://webmail.their-domain.com so that modern browsers don't throw hissy fits. Surely there is a way to get a free LetsEncrypt cert to cover it?

[jbwservices.com]

I setup my store with the $20.00 DNS Cluster and then applied a Let's Encrypt certificate to my store domain. That way my customers can access their email at https://webmail.mystoredomain.com and it is secure.

[clivejo]

Sorry, not talking about my reseller domain, I mean a customer domain.

[jbwservices.com]

My misunderstanding. It should simply require creating the subdomain webmail.their-domain.com, applying a Let's Encrypt certificate to the subdomain and then creating a CNAME record for webmail.their-domain.com pointing to webmail.supremebox.com or the appropriate webmail address.

[clivejo]

Tried that too, but Firefox throws "Warning: Potential Security Risk Ahead" because the LetsEncrypt cert is for supremecluster.com