Or you could just not send spam in the first place.
Anyway long story short, Mailtrain sounds interesting if it can solve this issue... but it's really not just spam that gets blocked as spam these days, its a major pay to play game and its the email companies that are getting paid, not the people getting the emails.
You could also take a look at Mailgun, which is more expensive than SES but might work better, and Mailtrain has Mailgun integration. In either case, you could look at adding a dedicated IP for your lists, which would help for deliverability, but increase costs: IPs are 24.95 a month on SES, and 59 a month from Mailgun