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Emails bouncing back


I am getting bounced back emails from a certain btinternet.com email account. The message I get is...

The reason for the problem:
4.3.2 - Not accepting messages at this time 421-'4.7.0 [TS01] Messages
from temporarily deferred due to user complaints -

Thanks in advance

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JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018
You want to make sure you have Reverse DNS lookup working, but that does not appear to be the issue here.

It appears that the target email system does not like you and the reason is normally excessive emailing or spam from the source.  

Check that email relaying is turned off on your end and then contact Support for the target email system and ask them why they are bouncing your emails. Go from there.

... Thinkpads_User
I'd agree with Thinkpads_User - your email server is sending excessive emails, to correct this check the email flow from your account to theirs using the following cmdlet

Get-MessageTrackingLog -Resultsize Unlimited -Server "Name of Hub Server" | where {$_.Recipient -like "*@btinternet.com*"} | FT Sender,Recipients,Time*

With the help of the result of the above cmdlet, you'll know how many emails are being generated for this domain.

Alternately, contact the IT of this domain to gain more information about such rejection.

David AtkinTechnical Director
Top Expert 2015

Go to mxtoolbox.com and verify that your domain is not on a blacklist.

You may have been added to BT's IP block list.  If this is the case then you may have to contact BT and verify the nature of the 'user complaint'.


Thanks for the advice

Exchange_Geek - Im not sure how to use the cmdlet that you mentioned. Can you elaborate on that for me please?

Scorpeo  - According to mxtoolbox, we are on a spam list Spamhouse-ZEN
Technical Director
Top Expert 2015
Hi Scott,

Okay - You need to remove your domain/IP from Spamhaus's black list.  See here:

You have yo type in your IP/domain and then go through the form.

To use Exchange_Geeks cmdlet you need to use the Exchange Shell.  Type in the command (replacing the hub server name with your exchange server name).  Can you confirm the Exchange version that you have?  I believe that command will work in Exchange 2007/2010.

Doing a little more digging though, the IP address is a KC address.  It maybe worth forwarding the error message to internet-support@kcom.com and ask them to comment on it as well. - They are genuinely quite helpful (we deal with them alot).


I have now got myself off the Spamhaus blacklist and informed Karoo about it. They also know about it too and they were making steps to sort it out. Spamhaus were blacklisting a range of IP's that Karoo were giving out.

Thank you all very much for helping me in this matter. 10 out of 10
David AtkinTechnical Director
Top Expert 2015

Glad you got it sorted Scott.