Towards brevity on tags on the subject line, I suggest dropping the word 'message' from the tag. So messages tagged as: "(someidentitystring: message 19 of 20)" would read: "(someidentitystring: 19 of 20) - the word "message" is quite redundant!
In fact, it could even read: "(someidentitystring: 19/20) and convey the same information!
Cheers again - I'm loving SG - and I encourage all users to donate! I'd like to see this service be around in perpetuity!