I'm communicating with one company via e-mail. It worked a few days ago but tommorrow I sent them an e-mail and I received e-mail with error message:
Your message for <name@company_name.com> from 2011/04/12 could not be delivered. Reason:550 smtp; 550 5.7.0 Your server IP address is in the SORBS DNSBL database. Mailbox unavailable.
Does it mean that something happened on their side? Could you explain me what happened? What is SORBS DNSBL database?