can't send email on certain accounts

[mdcrhodz]

Sorry for posting this topic again,

LOG:

Recipient address rejected: unverified address: hostmail.domain.com[ipaddress]refused to talk to me: 550 Service unavailable; Client host [ipaddresss] blocked using Trend Micro RBL+.

Is it because that trend Micro marked us as spam?
is it my fault? There are 2 more same emails that we can't send.

[Dirk]

it looks that way, yes.
There's commonly a URL also in the logs for further information, that should help resolve it. As for why you'd be on the list in the first place, could be many things. I remember that aol often check the reverse dns lookup on the mail server, so if you are sending from mail.mydomain.com but the IP address of that server resolves back to blah.blah.internetprovider.net then aol would block you.

Start of investigation would be at Trend though.