Setup Email server. Clients can receive but not send emails

If you run the following on your Linode, what log messages show up in /var/log/mail.log? (Make sure you pick a destination address that is external; i.e., not one that your Linode receives mail for.)

/usr/sbin/sendmail -ti <

That command worked from the server. Below is the output. I guess, my new question is, how can I get my external client to connect to the outbound mail server securely?

May 22 18:35:21 raidZend postfix/pickup[6593]: 8B09679039: uid=0 from= <root>May 22 18:35:21 raidZend postfix/cleanup[6962]: 8B09679039: message-id=<20130522223521.8B09679039@raidZend.raidgroupllc.com>
May 22 18:35:21 raidZend postfix/qmgr[31985]: 8B09679039: from=<root@raidzend.raidgroupllc.com>, size=346, nrcpt=1 (queue active)
May 22 18:35:21 raidZend postfix/smtp[6965]: 8B09679039: to=<a2ron44@gmail.com>, relay=gmail-smtp-in.l.google.com[74.125.134.26]:25, delay=0.39, delays=0.03/0.01/0.02/0.34, dsn=2.0.0, status=sent (250 2.0.0 OK 1369262121 d10si3397320yhd.192 - gsmtp)
May 22 18:35:21 raidZend postfix/qmgr[31985]: 8B09679039: removed</a2ron44@gmail.com></root@raidzend.raidgroupllc.com></root> 

Ah, this sounds like more of a Dovecot problem. I'm not very familiar with that. I would suggest trying to send something from your mail client and checking the logs (not sure if Dovecot logs to mail.log or somewhere else).

You may want to see if something is even listening for client connections on port 587 (netstat -lvpnut | grep 587 should return an entry with "0.0.0.0:587" and/or ":::587"). Next would be to make sure your firewall allows traffic to that port.

I will keep looking! Thanks for the help