Using SMTP (soft bounce) error codes to determine if an email hit a SPAM filter
Using SPAM feedback loops from ISP’s. A Feedback loop is an information provided by the ISP if a customer marked an Email as SPAM. The feedback loops define the complaint rate and the risk that the respective IP is being blocked. Not all ISP’s provide feedback loops.
Accounts with excessive SPAM related bounces
At this point, Sinch E-mail 365 does not have a policy on inactivating an account with excessive bounces due to SPAM. Our approach is to work with customers in reducing the SPAM footprint and move towards a dedicated IP address mechanism to support such sending domains with excessive bounces.