Email rejection with different IP address

IP Address Questions and AnswersCategory: IP QuestionsEmail rejection with different IP address
steve last asked 3 years ago

Hi, I am a user not a network person and am very puzzled by some odd behaviour. I have a number of email addresses and am finding mail from one of them keeps getting bounced back from some but not all recipients.

My laptop is in the UK and my current IP address appears to correspond to that, your search devices show it as being connected to a location which matches my ISP and email. I also have an address which is on my company's system hosted by Site5 in Dallas. Some but not all mail sent using this address (e.g. that sent to some hotmail recipients) gets returned with this message:
" SMTP error from remote mail server after MAIL FROM: SIZE=5089: host []: 550 SC-001 (SNT0-MC3-F14) Unfortunately, messages from weren't sent. Please contact your Internet service provider since part of their network is on our block list. "

My IP address is currently showing on my computer as something quite different but a similar problem a while ago had the same IP address as the problem. That tracks back to site5 in Dallas. However my local tech adviser says that the problem is with MY computer, it is not caused by anything on the system at Site5 which will just be the last one in the chain. E.g from my laptop >btinternet >site5> ownergroupscompany> site5> hotmail recipient . I appear to be able to send out using any of my other email addresses so I don't see how it can be a problem with my own laptop. Can you help or advise me on what's happening?

1 Answers
Shnerdly Staff answered 3 years ago

Thanks for your question steve last.

A lot of mail servers have blacklists for email domains. It's possible one of the IP's your sending email from is on the blacklist.

Some email servers use a whitelist, if your not on the list, you can't send them email.

Others use a filter that looks for a reverse DNS entry for the sending mail server. If the mail server name doesn't match the email domain, it rejects the email. For example, an email from whoever @ but the server reverse DNS is the ISP's Domain instead of

Know the answer? Login or sign up for an account to answer this question.
Sign Up