To generate your own certificate to use for SSL you can type the following command:

openssl req -x509 -newkey rsa:1024 -keyout /etc/mail/eximcert -out /etc/mail/eximcert -days 9999 -nodes

file1 and file2 can be the same file

The -nodes option is important as this prevents the key being encrypted with a pass-phrase which is not helpful for use with an MTA


The following line advertises TLS to all sending host and will preferably receive all mail over an encrypted session.
auth_advertise_hosts = *
Path to the certificates:
tls_certificate = /etc/mail/eximcert
tls_privatekey = /etc/mail/eximcert