This is a guide to updating your Linux server for SSL-enabled, IPv6-happy email transmission using sendmail! Here are the things you need to have already:
Add your IPv6 address to your SPF entry. For example, mine is:
v=spf1 mx a ip6:2a01:4f8:d15:788::2 -all
Add AAAA entries to your DNS. For each A record that you have, add an AAAA record with the value set to your IPV6 address.
Edit your sendmail.mc to reference your SSL certificate, eg:
define(`confCACERT_PATH', `/etc/pki/tls/certs')dnl define(`confCACERT', `/etc/pki/tls/certs/ca-bundle.crt')dnl define(`confSERVER_CERT', `/etc/pki/tls/certs/mydomain.crt')dnl define(`confSERVER_KEY', `/etc/pki/tls/private/mydomain-nopass.key')dnl
Configure and start saslauthd:
service saslauthd start chkconfig saslauthd onRun /etc/mail/make, then restart sendmail
After waiting for DNS propagation of your DNS changes, send an email to a gmail address and check your maillog (eg, /var/log/maillog). The log should show verify=OK and "Message accepted for delivery".
Sending a test email:
(echo: subject: test; echo) | /usr/sbin/sendmail -v -Am -i email@example.com