We were having problems sending as we utilize Microsoft Azure and Amazon AWS. The way we got to having outbound mail work 99.99% reliable and less in junk email was to signup for Mailgun. We pay $79/month and am super happy we did.

We did use Sendgrid but around 5-10% of the emails that went through them all went into junk email which was not a positive thing in our book.

With that said Mailgun does have some setup downs but it's a one-time-only thing so we were happy about that. In less than 16 hours we had 100 domains all setup and rocking. You can read my blog I wrote about it at https://www.businessyeti.com/Blog/Details/Migrating-To-Mailgun as I like to read about the pros and cons. 

Hi Ryan. Have you checked to see if you have a compromised account that may be landing your server on their blacklist? Also, have you checked to see if your server is listed on any other RBLs? A good site that I like to use to check is http://multirbl.valli.org/. If you see that your server is on any of the more popular RBLs such as Sorbs, SpamCop, Spamhaus, Barracuda etc.. then you probably have a compromised account. In order to find out which one is compromised, you can use our free Declude Hijack program. Declude Hijack prevents mass email from leaving your server in the case of a compromised account. It helps to keep your server off of RBLs. You can read more about Hijack here if you wish: http://know.mailsbestfriend.com/declude_hijack--1937121164.shtml. I hope this helps. Please let me know if there is anything I can do to help you. Thanks!

That's great news Ryan! I'm glad it is resolved!