Noted. Of course, the provider must know the IP is residential in the first place. From https://help.yahoo.com/kb/SLN26154.html https://help.yahoo.com/kb/SLN26

Noted. Of course, the provider must know the IP is residential in the first place. From https://help.yahoo.com/kb/SLN26154.html https://help.yahoo.com/kb/SLN26154.html > 553 5.7.1 [BL21] Connections not accepted from IP addresses on Spamhaus PBL > Dynamic or residential IP addresses as determined by Spamhaus PBL (Error: 553 5.7.1 [BL21]) > The Spamhaus PBL is a DNSBL database of end-user IP address ranges which should not be delivering unauthenticated SMTP email to any Internet mail server except those provided for specifically by an ISP for that customer's use. The PBL helps networks enforce their Acceptable Use Policy for dynamic and non-MTA customer IP ranges. --- I guess you're lucky enough that your IP adress has not been tagged as "residential" by Spamhaus.