Ok, thanks for the link - we can use that as a baseline for this
discussion.

What I'm after is: "Cause #4: Using a program that access the pst or ost
data."

I will definitely verify exactly what is running next time I get a call
about this, but I'm quite skeptical that it's some other program
accessing the PST.

So I read: "Restarting Outlook (after verifying it closed completely in
Task manager) may allow the mail to send"

Yes, that has seemed to do it sometimes. But what is the technical
reason why it even does this? My theory it that there some sort of lock
within the PST on that file that doesn't get released. Better yet, what
tools are out there to figure out what goes on within a PST? I'm not
talking about the pstscan tool, but some sort of utility to browse
through it. I suspect there isn't one?



Diane Poremsky [MVP] wrote:
http://www.slipstick.com/problems/nosend.htm