I'm currently sending a few 100 a day, expect to send 1000s of emails a day. Again, this is all opted in, but a lot of them still get lost in spamfilters, that'

I'm currently sending a few 100 a day, expect to send 1000s of emails a day. Again, this is all opted in, but a lot of them still get lost in spamfilters, that's the main problem.