I had a several Undelivered Mail Returned to Sender with my domain. This started happening at least 2 months, after I made an HTML signature.
It is possible, I don't know very well the sense of this. My e-mail signature only as a link with my site name and a PNG of brand logo (13kb). So if you guys could help me with this I will be very gratful.
This is the returned to sender (the most usual):
DOMAIN is blacklisted on Spamhaus - see www.spamhaus.org (in reply to RCPT TO command)
I checked my domain on their site and is not listed (idiot).