Based on this, you might get away with a custom template like this in /etc/e-smith/templates-custom/etc/dovecot.conf/:
Dovecot in SME server does not use dovecot.conf. See /service/imap/run. It's only using the /usr/libexec/dovecot/imap component of dovecot, wrapped via tcpsvd, stunnel-tls and imapfront-auth. IOW, it doesn't use the TCP listening, TLS and authentication code from dovecot, only the imap backend code.
To change the port, you need PORT=xxx in /var/service/imap/config.