Yes you can, assuming that appropriate firewall rules are in place for the mailbox to be accessed via MAPI/ GC lookups etc
Your issue is simply going to be performance. At that connection speed it is going to be very slow, and Im sure that bandwidth is not reserved for archiving traffic either. What you could do instead is send the journal reports over the internet to on-premise exchange (rather like EV.cloud) and then journal that local mailbox. You may lose the ability to do DL expansion if this is not part of the same org, but that isn't a great loss if you are using envelope journaling (which pretty much everyone is nowadays) since that contains the expanded DL member list.
Having said that, you will be ok if the message volume is really low. Have you worked out how much data you need to archive per day to see if this solution is viable with the connection speed you have?
Remember to use a separate task for this 'slow' link.
I'll just point out that since you are on exchange 2003, due to the way the items are processed from the journal mailbox, the performance will be better than exchange 2007/2010. If and when you decide to upgrade exchange, you will take a performance hit.