This is a list of settings for mail account setups for the most common email servers.

ISP Address Port Authentication SSL
AT&T pop.att.yahoo.com 995 Password Yes
smtp.att.yahoo.com 465 Password Yes
Comcast mail.comcast.net Password Yes
smtp.comcast.net 587 Password Yes
Sonic pop.sonic.net Password Yes
mail.sonic.net 587 Password Yes
AOL imap.aol.com 143 Password No
smtp.aol.com 587 Password No
Earthlink pop.earthlink.net Password No
smtpauth.earthlink.net 587 Password No
Gmail IMAP imap.gmail.com 993 Password Yes
smtp.gmail.com 587 Password Yes

You can also use Apple's Mail Setup Assistant which will give you the configuration for most of these common email services.