@iJoel You can do this by simply concatenating the intermediate and CA cert files into a single cert file. So, in the '.crt' file which you upload to Cloudron, it will have: -----BEGIN CERTIFICATE----- the *.foo.com certificate -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- intermediate cert -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- root cert if any -----END CERTIFICATE----- The ordering of the certs is important above.

@Peter-Newman did you manage to narrow this down any further? I can't think of an obvious reason this will happen. Please ping this thread again if you hit this issue.

I tried to reply via your support email already. The cert on your domain looks valid to me, so please clear your history and cache locally for that domain first.

Another option is to simply Disable mail and then Enable mail for the domain. This will effectively end up copying the certs.