I managed to fetch certs with opnsense acme-plugin. Already tested, works fine. I also managed to automate the deploy of the cert to mailcow. In the mailcow-docs is said:
"How to use your own certificate¶
Make sure you disable mailcows internal LE client (see above).
To use your own certificates, just save the combined certificate (containing the certificate and intermediate CA/CA if any) to data/assets/ssl/cert.pem and the corresponding key to data/assets/ssl/key.pem"
The copy of the certs from the opnsense is in:
/opt/mailcow-dockerized/data/assets/ssl/FQHN/
- ca.pem
- cert.pem
- fullchain.pem
- key.pem
Will that work?