Exchange online, outlook 2010 hangs after a few minutes and has to be shut down

After posting in outlook forum I was told I should post here.  Exchange phone support tells me it is outlook problem!  I just signed up for Exchange online and configured outlook 2010 with auto discovery. When I first start Outlook everything is fine. The folders sync and are up to date. I can send and recieve emails, etc. After about five minutes or so when i try to send email Outlook hangs as soon as I press send button. The only way to get out is to cancel server request or shut down outlook completely. Once I cancel server request the mail goes to outbox and sits there for ever. the only way to send the email is to close and reopen outlook. Again it works for few minutes and then the same.

I am using Win 7 pro (i7 with plenty of RAM) on a domain running server 2008 R2 (Xeon). Also using MSFT security essentials on workstations. All machines are up to date with all the updates. I have tried deleting old proofiles and making new ones. I have done DNS flush, repair office, remove and reinstal office. I have tried this on different machines on the network and is the same problem with all of them. I have tried gmail both IMAP or POP setup and none of the machines have a problem. I have even tried turning off the firewall but no luck. My laptop outside the domain works just fine (similar setup Win 7 pro and outlook 2010). I have spent several hours with Exchange on line tech support and have tried all the remedies described above several times. Nothing has worked. They tell me it is an Outlook issue since the exchange works both on the portal and laptop. I even installed Office 2013 on one of the stations to see if that will remedy the problem. No luck.

Help

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Ramin Mahallati