1. Most important item is country support as not all aggregators are
supporting all countries or may have limited support (e.g. no MO) in
some countries.2. No, there is no official list. You habe toncheck for
an aggregator supporting SMPP protocol.3. No idea, I guess you need to
search in the internet4. This is working via the SMPP protocol, namely
using SUBMIT_SM (send message) and DELIVER_SM (delivery status response
from aggregator) technical messages.5. Only SMPP for now