I’m sharing this guide because I spent a lot of time troubleshooting SSL errors while setting up Poste.io behind Dokploy. If you are using Dokploy, you likely noticed that the Let's Encrypt certificates managed by Traefik work perfectly for the web dashboard but aren't automatically applied to the mail server ports (25, 587, 993, 995, etc.). This leads to "SSL/TLS Handshake" errors in external clients like Gmail or Outlook.
When trying to generate certificates inside Poste.io itself using the built-in Let's Encrypt client, I constantly hit this error:
LEScript.ERROR: 400 ... Unable to update challenge :: authorization must be pending
Instead of forcing Poste.io to get its own certificate, this method "feeds" Dokploy's existing certificates into the Poste.io container. This ensures that the Full Chain (Leaf + Intermediate certificates) is present, which is r
