IMAP and SMTP AUTH using sendmail?

[Belmin]

I was thinking of installation IMAP and SMTP on my FC4 box. I haven't 
used sendmail for anything more than PHP's mail() function but it seems 
to be the software of choice?

1) I wanted a rundown of what would I need or maybe a HOWTO? Using 
google, I found some HOWTO documentation but they are vague as far as 
AUTH and I'm not sure of the terminology used. Maybe someone knows of a 
more apropos ( ;-) ) HOWTO?

2) Should I stick with sendmail? Any alternatives? What benefits would 
do they offer? How would that change my PHP setup?

3) As far as SMTP and IMAP, I wanted to use username/password AUTH with 
some type of encryption (don't want login information to be sent 
cleartext) since I will be accessing the servers remotely. Assuming I 
stick with (if I could) sendmail, how would I accomplish this?

4) Adding accounts/mailboxes w/o adding users to my linux box. Again, 
assuming I stick to sendmail.

TIA!