I didn't know that, thanks. I figured you'd get put on the list for EHLO'ing with a domain name that doesn't have a DNS A or MX record pointing to that IP address (or one that doesn't have a DNS record at all), but didn't think the lists were that strict.

Luckily my ISP ( https://www.plus.net/ ) is one of the best for technical support - when I built my server I asked them to change my PTR record and they did it within 12h - many ISPs won't let you do it at all.

EHLO based blocking is really useful for mail servers - mine received 30 messages yesterday, 11 were rejected because the client didn't EHLO with a FQDN, a further 10 were rejected because the hostname couldn't be resolved.