Please follow these instructions to install your SSL certificate on Dovecot IMAP Server:
1. Once you received your SSL certificate by e-mail, please copy and paste it into a text file and save the file as sslcertificate.crt (Include the tags -----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----) in your OpenSSL certs directory (usually /usr/local/ssl/certs/).
2. /ROOTS|Get your intermediate certificate. Copy and paste the contents into a text editor and save it as intermediate.crt in your OpenSSL certs directory (usually /usr/local/ssl/certs/).
3. In the Virtual Host settings for your site, in the dovecot.conf file (usually located in /etc/dovecot/), add the following SSL directives:
protocols = pop3s imaps
#debian etch ssl paths
ssl_cert_file = /etc/ssl/certs/sslcertificate.crt
ssl_key_file = /etc/ssl/certs/mail.yourserver.com.key
ssl_ca_file = /etc/ssl/certs/intermediate.crt
4. Save your dovecot.conf file.
5. Restart.