When I was using NetBSD in 2001 I actually liked the built-in "mail" command to read email. It was very minimal. Sadly, I could never figure out how to handle attachments with it.
"mail" is actually a fantastic interface to an email box assuming you don't receive very much mail. I still use it for things like sending myself an email notification when a long-running job is finished.
Maybe this wasn't the case back then, but with the mailx the comes with modern Linux distros you can attach files using the -a flag
