Our outbound emails—just regular daily emails, not newsletters or promos—are getting silently dropped by some spam filters. They aren't ending up in spam folders either, just completely dropped. Our domain has been around for almost 10 years, and we have had no issues sending and receiving email until recently. We don't send out any newsletters or marketing emails. These are just daily business emails that are getting dropped.
We discovered that our domain didn't have SPF, DMARC, and DKIM set up. I have set that up, and verified that they are correct, but now over a week later, and emails still aren't being delivered reliably to certain recipients
I'm somewhat technically savvy, but not an expert in email deliverability. I had my coworkers try removing their email signatures, and reducing attachments to max 1 per email, and those emails did get delivered to the same folks that were not receiving them.
But even emails on a thread where someone else's signature is present causes our outgoing mail to get dropped. In the meantime, we've had to scrub each new email in the thread of any signatures or attachments
I checked our domain and IP against blacklists, and nothing came up. I also set up google Postmaster tools, but nothing is coming up.
I've had the affected coworkers try from different email clients, from the browser, from different IP addresses, etc. No change there.
At this point, I'm really not sure what else to try. I think we should hire an expert, but I don't even know where to look for such a thing.
Any help?