Hi, I own a mail server typically used for mass mailing. All servers are hosted in Amazon EC2. All the SMTP dedicated IPs are Amazon Elastic IPs. Have good experience in mass mailing using Mandrill (which is no more), SendGrid. The SMTP and tracking services are all coded in java. If the emails are transactional (like, order placement, welcome, forget password) there is no limit on the sending rate. If it is promotional (in initial days) the limit is 15k per day/per domain. The limit will be increased on further days. If you opt for dedicated IP, (of course, I can provide you with) there is no limit on the emails since the reputation management is completely independent. Currently implementing marketing automation (like send emails based on user engagement time, linking with social profiles, etc. to get maximum inbox and CTR). can give you demo credentials to check the deliverability.
Thank you :)
Krishna (From India. Mobile +91 9789722162)