I am trying to find a cost effective approach to delivering a small volume of business emails, that offers a high rate of inbox deliverability. This question borders on a product recommendation, so I thought I would seek some recommendations here before trying it on the main site.
My company currently sends approximately 10k business emails per year from 10 different addresses (same domain), and we are presently using Office365. We require none of the features of Office365, except its ability to send emails and currently pay around $780/yr for it.
What I would like to do is to setup our own mail server (Postfix/Dovecot) and relay our outgoing business emails through a 3rd party SMTP relay. We already have Postfix running on our servers (which relays our transactional emails to Amazon SES).
In terms of getting things setup, I have no real issues. However, I do have an issue with inbox deliverability. Our business emails (i.e. personal/hand-written emails - responses to inquiries, etc.) need to end up in people's inboxes, and with Office365, we have not seen any of emails end up in people's spam folders. Sending from our own servers, we have been able to hit around 85-90% inbox deliverability (at less than 30 emails a day, we don't really send a large enough volume to build reputation on our IP addresses), but that is insufficient for business emails.
Most of the options we have explored (Sendgrid, Mailjet, Mandrill, SES) aren't really designed for this purpose, and have either directly or indirectly told us that they can't match the levels of deliverability we would see with Office365 or Google Apps.
So, my question is: how do small businesses with several employees, that send a small number of emails, send email in a cost effective manner. (With the side note, that we have the ability to setup whatever we need in-house).