I have exchange 2010 on server 2008 r2 and users are having issues sending emails with attachments. They are using outlook 2010 and every time they try to send a message with an attachment it gets hung in the outbox. The size of the attachment doesn't matter. It might sit there for a few hours before it is sent. However, if a user clicks send/receive all folders the message goes out. Send immediately when connected is checked in options and if I change schedule an automatic send/receive every 1 minute it gets sent after a few minutes. I've tried recreating a user's profile but the issue remains. I don't have any issues with my emails that contain attachments. However, I am a domain and schema admin. This happens to all users except for myself. It doesn't matter where the users are logged in. Size limitation isn't the issue because the message eventually goes out. The registry key below doesn't exist either. Key: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences Value name: MaximumAttachmentSize Value type: REG_DWORD I looked at the old case and it still seems to be an unresolved issue. http://social.technet.microsoft.com/Forums/nl/outlook/thread/2786061a-0410-479c-b430-29f665932791 I've searched through forums but have just seen the workarounds I have mentioned above without there being a resolution. Is there a fix to this issue?

That would indicate a networking issue, not an Exchange one. Do messages with attachments go out instantly when using OWA? You may want to try running this command on a test workstation and see if that makes things better: netsh interface tcp set global autotuninglevel=disabled Then reboot the workstation and then send the messages again

Hello, Please set event log level to high for information store service and check the result.Cara Chen TechNet Community Support