Ok, so we are running Office 365 2010. Microsoft just updated to Office 365 2013.
We have a large citrix environment. We use outlook without cached exchange mode to save room on our SAN in our citrix environment. We have a number of shared mailboxes that people use to reply to messages from outside clients. After the upgrade, these users are not able to send "from" these shared mailboxes in cached exchange mode. The message will just sit in the outbox and never send. If we enable cached exchange mode, the message will send.
We cannot enable cached exchange mode as that would require a rather large amount of storage space on the SAN, which is not an option. Any ideas why messages sent "from" a shared mailbox would send in cached mode but not in non cached mode?