[driaug]

Sorry about the confusing wording, with bounce I mean both hard bounces, rejects and complaints (they are all monitored appropriately). They are all taken into account when calculating the % because they all have impact on the domain reputation.

[djbusby]

But how do you know a message lands in the SPAM folder in Google?

[driaug]

I believe email clients send back a rejection if it landed in spam. It is one of the metrics AWS SES can track for you.

https://docs.aws.amazon.com/ses/latest/dg/monitor-sending-ac...

[troydavis]

Not quite. If a user actively reports a message as spam and also tells their service provider to report it to the sending service provider, then the sender will receive a report per RFC 6449: https://en.wikipedia.org/wiki/Feedback_loop_(email) , https://datatracker.ietf.org/doc/html/rfc6449. That's what SES exposes.

If you get more than a tiny handful of these, shut the account down. Whatever the reason, users don't want the messages and it'll destroy your deliverability quickly. Assuming the sender is legit, they need to figure out why users don't like the messages.

However, the much more common case is that a recipient's mail provider categorizes a message as spam on its own, without any user involvement. That's what parent commenters are referring to.

That can be for any reason. Maybe the user has reported similar past messages as spam. OTOH, maybe other users at the recipient service have had low engagement with messages from the same sender. Or maybe there was a sudden increase in sending volume from a given netblock or domain.

Emails that the receiving system categorizes as spam do not trigger any notification to the sender. Other than by trying to deliver messages to canary accounts or waiting for customer complaints, you won't know this is happening.