Help! My Emails Are Being Rejected!

Server Error 591

If you are getting something like the following then your local IP address has probably been used by another computer which was botted and sending out spam. Notice the error number (highlighted in red) is 591. Fortunately you can fix this error by clicking on the spamhaus link in your copy of the message and request delisting. Delisting will happen immediately.

Server error: ‘591 your host [] is blacklisted by (Courtesy message from PMBx)’

Next I suggest your surf over to to check that your IP address is not blacklisted. If you are listed in any of the blacklists shown, then you need to click on each blacklist where you are listed and follow their instructions to get yourself unlisted.

Then you need to make sure that your computer is not infected with virus or malware. Otherwise you are likely to be relisted as most listings are caused from personal computers that have been ‘botted.’

Server Error 579

The PMBx mail server has the ability to ban certain content such as profanity or key spam words. These RFCHeader mail server rules apply both to incoming and outgoing email so the banned content must be carefully crafted to only filter the objectionable email. Here is a classic error message on a Windows machine when you are trying to send email.

Task ‘ – Sending’ reported error (0x800CCC61) : ‘Your outgoing (SMTP) e-mail server has reported an internal error. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).  The server responded: 579 message content is not acceptable here’

The 579 error means there was a trigger word that is banned content. These words can be profanity for example or words or phrases that are specific to certain spam email. I found the particular log entry for your error. In this case it was this content (I’ve exchanged the letter ‘a’ for the @ symbol or you wouldn’t get this email of course):


That specific spammer has hit PMBx users with hundreds of thousand of spam for not only that particular product, but many, many more. I know that occasionally this can be an inconvenience for users and I do remove words from our list from time to time if there are problems, but this one prevents a lot of spam from getting into your mailbox.

Now in this particular case I was able to do some tweaking that would improve the filtering so that only the following were screened out.

  • Magic Jack
  • MagicJack

and not

  • Magical Jacks
  • Magic was a thing Jack liked to do to entertain the children.

Remember that the RFCHeader rules apply both to incoming and outgoing email. It is very worthwhile sending me the the 579 error notice when you receive them so that I can tweak the mail server. It is never my intention to stop your legitimate email from being sent or received. I investigate all of these errors. I do occasionally trip up and then even remove certain words from the list altogether if they encroach on the good email.

Server Error 450

This error is one that can be received if an email address is invalid or if the recipient is using greylisting. Here is the error message example.

Diagnostic-Code: smtp;host says:
450 4.7.1 <>: Recipient address rejected: Please try again later. For more info see <>

Notice that this error didn’t say that the email address was invalid. Rather it says that the address is being rejected by the server, but points you to the reason why in the URL to the page ‘greylist.php’ for more information. Following the link might help, but it may not.

Greylisting is rude and selfish in my opinion.

Failed to deliver

This error doesn’t have a code. It just says that it failed to deliver the email. This could be because the receiving email server was not responding because of an internal problem with its software. In this particular case it was because the email address was wrong.

Failed to deliver to ‘’
SMTP module(domain reports: no response

The mail server assumed therefore that the attempt to deliver an email was bogus.

This is a method of harvesting good email addresses by spammers. They have a large collection of possible email addresses and it sends each of the them an email to the mail server from which they are trying to harvest fresh, accurate emails. If the mail server responds with an NDR (non-deliverable recipient) then they scratch that email address off their list. If the mail server doesn’t get an NDR then it is good.

If the mail server however responds with this failed to deliver it could be that the mail server simply is not responding at all with any information that tells the spammer whether an email address is valid or not. However better mail servers tend to simply accept and discard the email so there is no response whatsoever and so the way this mail server is set to respond is still like an NDR.



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