You didn't specify operating system but for 500,000 users I wouldn't even go near Windows.

thanks for the feedback..we are a SUN shop so solarius is our OS of choice.

I use a healthy mix of Postfix as the mail server and Courier-IMAP for POP3/IMAP delivery. They both work extremely well.

Chris -- Chris Horry "Don't submit to stupid rules, zerbey@wibble.co.uk Be yourself and not a fool. PGP: DSA/2B4C654E Don't accept average habits, Amateur Radio: KG4TSM Open your heart and push the limits."