Captain Verify

A prospecting tool tries firstname.lastname@, f.lastname@, lastname.firstname@ and every other variant until an address responds, and the person being targeted usually knows nothing about it. On the sender side, the symptom is familiar: campaigns that land in spam with no one knowing why, and a hard bounce rate that climbs on contacts that were “found” [...]

A 550 5.4.1 bounce at a Microsoft 365 customer, while SPF/DKIM/DMARC authentication shows PASS. The rejection has nothing to do with authentication. The 550 5.4.1 code means the recipient’s address doesn’t exist in the receiving server’s directory, or access to it is explicitly denied. It’s a directory rejection, separate from sender reputation rejections. The context [...]

Your campaign goes out, part of the recipient list stays in the queue, and the log shows “452 4.5.3 Your message has too many recipients” while your emailing tool reports that everything is OK. The server is refusing part of the list in that SMTP transaction without closing the connection. Split the send into batches [...]

A Gmail address with an almost empty inbox can return a mailbox full on every send. The whole Google account is saturated: emails share their storage with Drive and Photos. On the campaign side, the result is a hard bounce rate that climbs while neither the content nor the IP has changed. Your sending tool [...]

Nobody suspects the signature. Yet it’s the one block your mail client copies into every outgoing email. A sales rep who sends 80 emails a day from Outlook broadcasts the same logo and the same links 80 times, which means 80 copies of the same HTML. “My campaigns end up in spam and I have [...]