YAM is one of the more recent mailers to come out of the Aminet archives and it's a gem.
Fairly small, it supports most of what people need such as automatic uuencoding and decoding of attached binaries, archived messages, forwarding, SMTP, POP3, pleasant GUI, excellent addressbook, mail spooler, forwarding, and so forth. It's also stable which, after my problems with earlier versions of Airmail, is a dream. The interface is much easier to install, set up and use than Thor, although there are fewer features built in. As with all good mail programs, YAM allows the user to define the editor used which means I can use GoldEd. Signatures can be defined from within the program, as can the quote character(s).
A further feature which seems to becoming standard in the Amiga world is a switch that converts the close gadget on the top lefthand corner of the window into an iconify gadget. This is really handy so you don't have to remember the hotkey or find the menu item that minimises the program everytime you use it.
The appicon also changes depending on the status of your mail. If you have nothing in your infolder, it shows an empty tray; if there's read mail then the envelopes in it face away; if there's new mail you get to see the stamps on the other side. Mail arriving in from periodic (user definable) checks results in a system beep so you're notified immediately. Nice for email junkies such as myself.
It's also MUI which for me is fine, but might annoy some people out there.
What's really nice is that it's registerware. Yes, for the cost of an email message that it composes automatically, the program will dispose of the requester asking you to register the program. That's all -- no money, no postcards, no beer or chocolate. Just one bit of email. To the financially strapped Amigan this is a godsend (and even for the not-strapped-but-tightfisted-amigan.)
I currently use a script that connectes Voyager and AWeb 2 to YAM, so YAM is used to send mail when one clicks on a MAILTO: link within the browser. It works quite transparently.
Mail is stored in individual files. This can slow loading a little but performance doesn't seem to be affected too badly. And it does mean that a crash while getting your mail doesn't result in a corrupted message database!
YAM doesn't do binhexing, PGP, ROT13, MIME, multiple folders or many of the other extentions that are coming into use these days although v1.3 due out soon is supposed to. If you do need those functions, my recommendation is to either use Thor, or set up some scripts within your favourite text editor to achieve the same purpose. It also doesn't import Pine formatted mail folders or their address books, so you'll have to re-enter the latter and forget about the former but again I believe this is going to be fixed in the upcoming version.
All in all, I'm very happy with this program and will continue to use it. Take a look -- it's not expensive :)