[no1youknowz]

Many of their IPs have been blacklisted by spammers.

When I last tried to use them for marketing purposes with paying clients, it was really hit and miss.

See below. They are old links, but serves my point.

[0]: https://forums.aws.amazon.com/thread.jspa?threadID=233001

[1]: https://forums.aws.amazon.com/thread.jspa?messageID=538207

[2]: https://forums.aws.amazon.com/thread.jspa?threadID=220517

[adrr]

Also if your sending that amount of emails, you want your own IP. Maybe even two IPs, One for transactional and one for marketing.

[robjan]

SES allows you to purchase dedicated IPs