Has anyone else with relatively large volumes of email seen a huge spike in rejections from AOL recently? There is no obvious reason why they are being rejected as it is a generic message: Nov 18 12:10:39 pp-serve02 sendmail[1391]: tAIHAcPT001383: mailin-04.mx.aol.com.: SMTP DATA-2 protocol error: 521 5.2.1 : AOL will not accept delivery of this message. Looking back through my logs, I can see we've always had a few, but we are now receiving a lot of complaints from users (physicians who cannot email their patients) and I see this, starting on Monday: syslog-2015-11-16 588 syslog-2015-11-17 1668 syslog-2015-11-18 1937 and I already have 55 for today. We have a whitelist / feedback loop set up with AOL, our IPs show clean with them and our DNS / reverse DNS has not changed and resolves properly. We did raise a ticket with them, but it seems to have gone to the usual /dev/null. To reply off-list, please remove the VERP -nanog from my email address,