First, exactly what is the security team requesting?
Are they saying that the Exchange server (or whatever) you're using as your relay will be configured to require authentication before accepting mail? Then you should probably talk with the Exchange and/or AD admins and have them configure a "service account" for your Sendmail. Then you can add the username and password for that service account to your Sendmail configuration, so that Sendmail will authenticate as the service account when sending mail to Exchange.
If you are using Sendmail to handle locally-generated mail only, you should then make sure that other people in the network (or worse, in the entire Internet) cannot use your Sendmail to inject email to Exchange for further delivery. If your Sendmail only listens for SMTP in address 127.0.0.1, you're probably safe.
OR
If your Sendmail actually accepts incoming email from the network, the security team might be telling you to set up authentication or stop running Sendmail. In that case, you may have a lot more work.
First, find out:
- why your users are using your Sendmail instead of using the Exchange SMTP directly? Can they switch to using the Exchange SMTP interface and the appropriate authentication?
- can your users handle SMTP authentication (and probably SSL/TLS encryption too, since authentication in plaintext over the network makes no sense)?
- if your users cannot use authenticated SMTP (e.g. because they are hardware devices whose configuration supports basic SMTP only), are they located in fixed IP addresses? Would it be acceptable if your Sendmail accepted email from those fixed IP addresses only?
- does the security team require you to use AD usernames/passwords for authentication, or is it enough to implement a separate list of Sendmail users+passwords in some other way?
MK
