Cannot Send Mail - Server "smtp" failed
I got the iPhone a week ago and I finally got my work email account to appear on iPhone via POP. But while I can receive email, I CANNOT reply or send email out. I've tried changing SMTP port from 25 to 587, 2500, and 2525 but am still getting the "Cannot Send Mail" message. Have also gone back in to Outgoing Mail Server settings on iPhone to turn SSL off and Authentication via Password.
Company email is hosted by PacificNet Hong Kong and I'm trying to access email in the US. PacNet tech support forwarded me this link as troubleshooting iPhone email set up: http://tinyurl.com/pacnethk
Out of curiosity, I took the settings and applied to Thunderbird and had no problems receiving or sending mail. Is it just the software on the iPhone or am I missing something?
Macbook, Mac OS X (10.5.6)