Setup a working Mail Server on my Ubunto 11.10 Rackspace cloud. Use PostFix & Dovecot & SquirrelMail. Work With Email Clients Also, Hourly Pay & Future Work!

Hi I'm looking for a part time assistant to help me with a project, I will pay hourly for the assistance. I'm a programmer on here but I'm getting really frustrated with the task of installing the webmail on the server. I've never done this before. A couple of days ago, I installed PostFix as the Mail Transfer Agent. Then I installed DoveCot as the Mail Delivery Agent. I then installed squirrel mail. I was able to send and receive email fine, except from an email client such as thunderbird. Oddly enough I was able to 'get mail' in the apple mail program, but not the thunderbird application? So I know my passwords and usernames were correct. The apple mail still could not send email though. I'm using a subdomain and all MX records are pointing to the correct IP address, but I'll have you double check everything. I made some changes in the [login to view URL] file for postfix and in dovecots preferences, noticed things broke, I turned them back to normal and now it's still broken! I can't check email now, I can oddly only send email from squirrelmail. This seemed to happen right after I added a new user to the system as well? Could this have screwed things up? I did a reboot and restart of all services, no luck. I am at a loss, I really need someone's help who is a pro at setting up there own server and in particular a mail server. Need help ASAP for a project I'm doing on here, so I'll pay well for the time. I want to learn how you fix it along with you on Skype if possible, so I appreciate English speakers.