What is a "delivered" email?

A delivered email is one that the receiving server accepted during the SMTP handshake. The server said "OK, I'll take it" and logged the message. That's it. That's delivery.

What delivery does NOT tell you: whether the email landed in the inbox, spam folder, or promotions tab. The server accepted it, but where it went after that is a different question entirely. This is why your ESP's "delivery rate" can be 99% while your actual inbox placement rate is 60%. The server took the email (delivered), but it didn't necessarily put it where you wanted it (inbox).

Here's the practical version. When you send an email, your server connects to the recipient's server and has a conversation (the SMTP transaction). If the receiving server doesn't reject it (hard bounce) or defer it (soft bounce), it accepts the message and returns a "250 OK" status code. At that moment, your ESP marks the email as "delivered." But the receiving server still has to decide what to do with it next. That decision (inbox, spam, promotions) happens after delivery, using filters, reputation checks, and engagement signals.

This distinction matters because "delivered" is often confused with "successful." If you're looking at a 98% delivery rate and wondering why no one's opening your emails, the answer is probably that most of those "delivered" messages are sitting in spam. Delivery and inbox placement are completely different metrics, and ESPs only report the first one automatically.

If you want to know where your emails actually land, you need to test inbox placement separately. You can check a sample campaign with seed lists (tools like GlockApps or Email on Acid offer this), or watch your open rates and complaint rates closely. Low opens + high delivery usually means spam folder. And if you're stuck figuring out why, our SOS hotline is free (and we actually answer).