The issue is not about sending email (switching providers). The issue is about our customers being able to receive the emails. If we send email to other email clients, they receive the message.
The issue occurs when our customer uses Gmail or any google product. The mail gets classified as spam in those cases.
A good guess is that Google/Gmail maintains their own internal private blocklists, and our domain is most likely on it (even if it is a false positive).
I Agree that marketing email are super obnoxious. In the very few instances that we send (e.g. black Friday), we include an unsubscribe link :)
Yes, we are informing our customers to flag us as not spam. However, our domain reputation is 100% (google's postmaster) according to Google's support, this doesn't seem to be the case.
We will continue informing our customers and helping them set filters so they can receive our emails (eg. forgot password and other important emails). But everything on Google's side is showing as OK and we are still left without an answer.
We have been trying to solve this with Google's customer support team. Every time they give a different answer. It almost feels as if they are taking a guess. They mentioned it was Sendgrid's fault and we should remove the service from the SPF. Then they mentioned it was because of TXT records, Low IP rating, etc.
How can we receive good customer support from Google?
Yeah, checked mail server IP and it isn't the issue. Our users are marking the email as not spam, but they have to do it for every single email.
10 days after our mail started ending in Spam, our domain Authority decreased. It should have been the other way around (First Domain Authority should decrease and then mails should go to spam).