On 31.08.2018 21:31, Michael Schumacher wrote: > certbot works only with ports 80 or 443? Can lego work with with IMAP > ports like 143 or 993? The documentation is not very clear. basically - independent of the client - letsencrypt will only support http/https or dns based challenges. so - if you want to get certificates for an imap only server, you will have to setup an webserver for the challenge. or deal with your dns server. best regards Ulf