[Maxious]

We've occasionally got bounces like "554 5.7.1 Service unavailable; Client host [54.240.27.56] blocked using dnsbl.sorbs.net".

Amazon say SORBS is worthless but unfortunately someone is still using them https://docs.aws.amazon.com/ses/latest/DeveloperGuide/blackl...

[spronkey]

Seriously, doing bulk emailing you find that mail services are often the dustiest, cobwebbiest things on the internet. I swear some of these things have been sitting untouched for literal decades.