Not my project! Given the benchmarks Exim would not be first choice MTA in a perfect world. You have to wonder if trying to send several 1000 emails to say gmail would be accepted. Certainly when I hooked thunderbird up to the POP side of it I got throttled to 3 email downloads per minute. Sure POP download if different to SMTP upload but Google for example seems to throttle anything that looks fast and automated across all their services, at least in my experience. Although I have no evidence to prove it I would be far from suprised if all the big free mail services did not throttle what might easily look on the surface like a spam bot.