I know that this topic has been covered many, many times as I've been reading & re-reading the threads & documentation for several weeks now and still can't grasp how e-mail is supposed to be configured. I'm not a newbie to e-mail & webhosting as I've been administering a Windows based Hosting Controller/MailEnable setup for three years. MailEnable allows me to have [email protected] as the login and that's what I've become used to. I am somewhat of a newbie to Linux, but I can follow well laid out instructions such as the "Perfect Setups". I followed the perfect setup for Centos 4.4 on a virtual appliance in a NATed environement behind an EFW firewall. I'm using 1to1 port forwarding to get from my external IP to my internal IP. So far I'm only using web & FTP as I'm not ready to transfer DNS & email into my NAT and everything is working great. So on to my e-mail questions. The biggest problem I'm having is understanding how the e-mail logins are configured. I think I understand that the e-mail login ties in to a unix username. I'd rather not use a prefix at all, but if I happen to have two users by the name of "John Smith" and want to maintain consistency among usernames I have to have one. I've changed the prefix of my accounts from web[WEBID]_ to [DOMAIN]_. This allows me to have [email protected] & jsmit[email protected] but I think I might possibly run into problems if the combined domain name & username have more than 32 characters. When I configure an outlook client it doesn't let me login with these e-mail addresses, instead I have to use domain.com_jsmith as the username. This is confusing since the Squirrelmail package allows a user to login with the e-mail address. Is using the e-mail as the login not possible or did I configure something wrong? What does editing /usr/lib/sasl2/smtpd.conf accomplish? I installed the Squirrelmail package from ispconfig.org and am able to login with [email protected]. I send an e-mail to one of my accounts on another server and it shows up as being from [email protected]. I go back in to Squirrelmail and configure my from and reply-to options and now the test e-mail shows to be from [email protected] however the header shows the e-mail to be from domain.com_user. I also don't like this configuration because it requires the user to go to http://hosting.domain.com:81/squirrelmail/src/login.php to access their e-mail. The "Squirrelmail in 10 Steps" setup is close to what I'd like, but not quite. If I create a site mail.domain.com and add co-domains for every other domain that wants webmail access, is there a way to have the domain name setting in config.php be pulled from the host header value? If this type of setup isn't possible, are there any MailEnable-like linux e-mail products that allow domain admins to cofigure and maintain their own e-mail usernames, groups, listservs, etc from a web interface? If we go with an external mail application, then what is the purpose of setting the sites to "External Mailserver"? Thanks.