You should check to see if the messages that are being sent contain any links that would be considered questionable/spammy. You can also try taking the content of one of the messages and checking it’s spam assassin score ( https://spamcheck.postmarkapp.com ). Source: over 2 years ago

Build a clean email that passes a spam check with flying colors (https://spamcheck.postmarkapp.com/) then use a warmup service like lemwarm, inboxally or neverspam as mentioned in the other comments. Source: almost 3 years ago

The issue sounds more email centric. You're likely hitting the Apache SpamAssassin limit on the remote email servers. Use https://spamcheck.postmarkapp.com/ to check the score of emails you've had declared spam, and follow recommendations to improve. Source: about 3 years ago

Thought I would drop this here for those looking to unsubscribe. Doesn't work 100% but has helped me clean a lot out. https://unroll.me/. Source: 12 months ago

Hey. I hope you get access to it soon. I'm developing a plugin similar to unroll.me - it will help you to unsubscribe from those unwanted pesky emails automatically. To be honest, I'm developing this for myself, I'm not sure if I would even release it publicly since most people are not comfortable sharing email access with 3rd parties (and rightfully so). Source: 12 months ago

Most of these are just newsletters and typical spam. They have your email to send you this stuff from when you made your old accounts. You can unsubscribe from each service manually (usually a small "unsubscribe" link at the bottom of each email). Or try this tool to unsubscribe from most of them quickly. Source: about 1 year ago

Another vote for unroll.me. Only way I'm able to handle my email. Source: about 1 year ago

Have you ever used https://unroll.me/ ? Source: about 1 year ago