DomainKeys is an e-mail authentication system designed to verify the DNS domain of an e-mail sender and the message integrity. The DomainKeys specification has adopted aspects of Identified Internet Mail to create an enhanced protocol called DomainKeys Identified Mail (DKIM). More about DKIM another day.
But if you have a newsletter email list or marketing email list, when you send out your mass emailing’s, the big providers will push back on you with an error email message like:
Remote host said: 571 Email from 72.167.234.232 is currently blocked by Verizon Online's anti-spam system. The email sender or Email Service Provider may visit
Verizon Online and request removal of the block. 110826 I'm not going to try again; this message has been in the queue too long.
Connected to 205.188.59.193 but greeting failed.
Remote host said: 421 4.7.1 : (DYN:T1)
AOL Postmaster | Postmaster / AOL SMTP Error Messages
I'm not going to try again; this message has been in the queue too long.
421 DYN:T1 - The IP address you are sending from has been temporarily rate limited due to lack of whitelisting, unexpected changes in volume, or poor IP reputation.
421 CON:B1 - The IP address has been tempfailed due to a spike in unfavorable e-mail statistics.
They are looking for you to implement some anti-spam technology, SPF as I mentioned in the previous post, Domain Keys and DKIM to name a few.
DomainKeys is real easy to implement here at HostNexus, go into Plesk / Mail Accounts / Mail Preferences / check off Use DomainKeys.
Then send an email to
auth-results@verifier.port25.com and see if your SPF and DomainKeys PASS.
Linear Mode
