I have a colleague with Outlook 2010 on an i7 with Windows 7. When he attaches a file (from the network or local) it takes 6 to 10 seconds to complete the attachment. I created a 2nd profile on his computer, configured the Outlook to the same pop3 and imported his exported pst file. Attached to the same network share, the attachments are immediate. I tried Outlook in safe mode on the original setup but it's still slow. I have found if I drag the attachments from Windows Explorer instead of using the Outlook "attach file" the attachments are instantaneous. I told the SEP to not scan, but that did not help. Any ideas of what else I can do to troubleshoot this? Is there a way to change what Outlook uses to attach a file (for instance using explorer instead)? I tried running Process explorer and Process monitor, but there is just too much information to see what is causing this.
I think it's somehow related to the network drives but I'm not sure exactly what. As larry mentioned, mapped drives cause this problem - Outlook tries to ping to every drive when you add or save attachments and I think it's having problems in the one profile.
Interestingly I found that if you open Windows Explorer, find the attachment on the network, and drag it to the email that is already open, it is instantaneous. It's only slow if you use the attach option.