Overview
The motivation to configure sendmail as a client for Simple Mail Transfer Protocol with SSL (SMTPS) came about when I switched ISP's and the new service required authentication as well as the use of port 465 to submit an email for delivery. The old ISP permitted the use of port 25 as long as your IP address was part of their network, whereas the new service blocks that port to outgoing traffic. Setting up SMTPS is fairly easy to do using a client like Evolution, however, it is not quite as straightforward to configure sendmail to do the job. The reason why I needed sendmail was to allow my home server to send email using the PHP mail function from a web page. One of the uses of this server is as a platform for website development and testing.
When researching this topic I found a number of helpful sources on the internet. One of the problems though is that they didn't have all the pieces or something was a little off. Two very helpful sources where:
- Qiao Yang's Blog - Sendmail + AUTH +SSL tunnel -> ATT Yahoo! and AT&T Yahoo Email Address Verification and Sendmail
- SMTP AUTH in sendmail 8.10-8.13
Left To Do
- Install and configure stunnel
- Configure sendmail
- Firewall
- Dynamic DNS to allow for address verification
- Email address verification on ISP
- Double check security for any holes
- Look at the possibility of using submission Port 587