In this latest post of a series of blog posts where we attempt to demystify the most common SMTP error codes, today we discuss Verizon's ubiquitous rejection code:
Email from xx.57.168.45 is currently blocked by Verizon Online's anti-spam system. The email sender or Email Service Provider may visit http://www.verizon.net/whitelist and request removal of the block. 123929
What does it mean?
Verizon's email systems have rejected your message because the IP address of your mail server has been blacklisted by Verizon's internal IP reputation system. It's likely that your mail server is blocked because of recent bad behaviour such as sending spam, or email content about which Verizon customers have complained.
Verizon describes the error on their web page:
To protect our members and our network from unsolicited e-mail (spam), Verizon Online has put measures in place to restrict the distribution of e-mail containing spam and potentially harmful viruses to our members. If we review a restricted e-mail address or domain and determine, based on the information available, that it does not pose a current unacceptable risk to our members or our network, the e-mail address or domain can be "whitelisted" and, therefore, e-mail delivery will be allowed to your mailbox.
What can I do?
If you are confident that your mail server is not sending Verizon spam or other objectionable content, then you can request that Verizon add its IP address to a whitelist. You will need to fill in their and follow their recommended best practices.