I've just noticed that mails are returning due to the recipient's mail server refusing it because it suspects my server as being spammed. Here is the error message below :
I am behind a NAT and i've noticed this on my test server this afternoon. I had to delist my ip address on spamhaus.org.<email@example.com>: host mail.domain.com[ipaddress] said: 591
firstname.lastname@example.org Your message has been refused because your server
at [ipaddress] is blacklisted at sbl-xbl.spamhaus.org. Please contact
your system admin or ISP.. (in reply to RCPT TO command)
Anyone suspect why i have these mails refused ?