I use Outlook 2000 on my desktop and Outlook 2003 on my laptop. In
each case, I have it configured to send/receive mail from about a dozen
accounts on two different servers.

On my laptop, I am able to both send and receive mail when I am
connected via broadband, but only send when on dialup. I have noticed
this in hotels and at worksites. For example, when staying in a hotel,
if I dial in (I use AOL), I can receive mail but cannot send it.
However, if I decide to purchase the hotel's broadband option, I can
both send and receive. I found the same thing while working at a
client. I am staying at an apartment owned by the client where there
is no broadband, and at the apartment I cannot receive mail through
Outlook. However, in the office they connected me to an external
broadband connection (not the office network, as I think that would
have had outside access restrictions) and I could both send and
receive.

Any ideas?