Inbound mail bounced.

[jbuchanangb]

I have been notified that an email addressed to my Tiscali account was bounced back. The sender received the following bounce message:

A message that you sent could not be delivered to one or more of 
its recipients. This is a permanent error. 

The following address failed: 

    my.username@tiscali.co.uk: 
        SMTP error from remote server for GREETING command, host: mx003.tt.xion.oxcs.net (135.125.7.163) reason: 550 5.7.1 Connection refused - [212.227.126.133] blocked by Validity - https://senderscore.org/blocklist-lookup/ - OXSEU001_102 - https://postmaster-oxseu.vadesecure.com/inbound_error_codes/#_102 

Can anyone explain why this happened?

[amahle-TT]

Thank you for letting us know, you’re correct that changing the port number from 587 to 465 wouldn’t resolve an issue related to an IP address being blacklisted.

 The bounce message clearly indicated that the sender's IP was blocked by the Validity service, which is a common measure to prevent spam and ensure email security.

It's good to hear that you were still able to send emails after changing the port, but the underlying issue of the blacklisted IP remains important. If the sender continues to face delivery problems, it would be beneficial for them to check their IP status and work on getting it removed from any blacklists, thanks.

[jbuchanangb]

I spoke to the technical support for the mail service, and they tried to tell me that I was using the wrong port no for outbound mail to their server. As if that would cause the "Validity" server to report that their mail server IP address was blocked!!! Anyway I changed the port no from 587 to 465 and it still sent email OK. So it's no worse. But I don't believe that was the cause of the problem. This was not any sort of error caused by TalkTalk. It was TalkTalk's mail service rightly blocking mail from IP addresses on a blacklist.

[amahle-TT]

Alright, thank you for letting us know.

Take care

[jbuchanangb]

Thank you for the explanation. I have received another email from the same originator, and when I look at the detailed message headers I can see that this other message was sent from IP address 212.227.126.134. 

As I have an account on the sender's mail server, I decided to send myself a test message. This has failed, with a similar failure message to that previously reported, but this time with IP address 212.227.17.10

I will try contacting their support desk.

[amahle-TT]

Hi there @jbuchanangb, thank you for reaching out.  The SMTP Error: The error message specifies a 550 5.7.1 Connection refused. 

This typically means that the receiving mail server (in this case, Tiscali's server) has rejected the connection attempt from the sender's server.

Blocked IP Address: The message mentions that the sender's IP address (212.227.126.133) is blocked by Validity. This suggests that the sender's server has been flagged for some reason, possibly due to spam reports or other issues that have led to it being blacklisted.

So, the sender should check your IP address if it is indeed blacklisted or not, thanks.