So ive been doing more TLD mailing as of late and wile doing data QA, I noticed a pattern in many bad emails I was getting. They were emails that looked like this: [email protected] [email protected] [email protected] So what I did was jumped in excel and made a few list where I did this @1hotmail.com @2hotmail.com @3hotmail.com . . . . @10000hotmail.com so I created 10000 addresses for each of the major TLD domains and added them to my suppression file. I have already noticed this trick has caught many bad emails and improved my bounce rate slightly. Hope it helps you guys too!