Hi, We use smarter Mail8 with 90 outgoing treads , using C# code to submit EML files in smarter mail spool, retry is 240 minutes. Yesterday it took extra 4 hours to send out our emails. I checked the logs and found over 50,000 records with error 421 e.g gray listing for AOL users only. Please advice , does bounces slow down smarter mail spool ? Should we change configuration ?