Absolutely confident. Yesterday I decided to try out a theory of pulsing messages out in small batches. Worked a treat, incidentally. However, getting the initial configuration right was a pain in the arse.
I figured 8 emails every 5 minutes would work AND be under the 100 an hour. However, on the first test of the batch send (so about 5 emails sent by that point) it sent 10 (I was testing if it worked, not the exact numbers) and then suspended the account.
After numerous attempts over the rest of the day I eventually got down to 7 emails every 5 minutes (sent in the space of 1 minute as any longer and the CRON job times out) and it works a treat. Been doing those 7 emails every 5 minutes for 28 hours now.