A Few Emails Bounce with Error 451 4.4.0 and 5.5.4

[PaulO99]

Our internal Exchange 2010 email server has been sending emails for 5 or so years with no real problems.

The domain name is registered with EXA Networks. Even when we changed our ISP from EXA Networks to British Telecom earlier in the year there were no real problems, until now.

We are getting emails bounced back from recipients with different ISPs but with the same error message.

 

"451 4.4.0 primary target ip address responded with 554"

 

Our domain name is "halstead-school.org.uk",

 

Our MX record is reported by ns1.exa-networks.co.uk as

mx.exa-networks.co.uk 82.2xx.x.4

 

Our Reverse LookUp is reported by ns21.bt.net as

host81-14x-xx-xx7.in-addr.btopenworld.com 81.14x.xx.xx7

 

As the emails have been working I'm not certain what needs to be done to resolve the situation

 

Regards,

 

PaulO

[Geoff]

MXtoolbox have a good testing tool.

 

halstead-school.org.uk Domain Health

[PaulO99]

Thanks Geoff.

I've had a look at MXToolbox before and apart from the 'dmarc' record and website certificate (hosted by others) there are no errors.

I'm not sure about the importance of 'Reverse DNS does not match SMTP Banner' from what I've read and am not certain what to do to correct it'

Regards,

PaulO

[Geoff]

You can't do anything about the banner as it's not your SMTP server. You can do dmarc, spf and domainkeys though if you have control over your dns records.