Sender's emails keep getting identified as spam by a remote server, but they aren't They never land

[jfeat]

A sender sometimes get this message when trying to send me emails:

"The response from the remote server was:

550 5.1.0 Q5Tbp0M79KUQj Sorry, we’ve identified a number of outgoing emails from your email provider [ie. sender's] as spam so we haven’t been able to send your email to its intended recipient. Please try again later or using an alternative email address. For more information visit our help article (link: help2.talktalk.co.uk/i-cant-send-or-receive-emails) (TT406)"

is there anything TT technical support can do to fix this? How do I add the sender's address to a friend's list? The help article returns a 404 Access Denied erro

Thanks

jfeat

[Gondola]

Google's Gmail is one of the world's biggest sources of spam largely because of the sheer numbers of Gmail accounts that are created by or hijacked by spammers. But Google have an active anti-spam team and hundreds of servers to use so that when one server IP address does get blocked there are plenty of others to use.

Is your contact sending from Gmail using a webmail sign in or via an email app or email software on a user device. If sending from email software then the originating IP address will be the public IP address that their ISP has allocated to them or the IP address of a VPN host if a VPN is active.  That public IP address may be on a blacklist because a previous user was detected as sending spam. VPN host IP addresses are often on spam blacklists because spammers use public VPN's to hide their location.

So, in summary, using Gmail webmail to compose and send an email is least likely to be blocked. Can't guarantee Gmail won't ever not be rate limited by TalkTalk which means applying a limit on numbers of Gmail emails inbound as a way of controlling excessive spam.

[jfeat]

Thanks Gondola, very helpful

The sender's email domain is gmail.com

I can't imagine that they have ever been involved in sending out spam.

jfeat

[Gondola]

The help article no longer exists but the bounceback error message is accurate.  TT406 means that the sender has been blacklisted for sending spam and as a result TalkTalk is not prepared to accept the inbound mail. Which is why it never arrives.

There is no whitelisting, sometimes known as safe senders listing, in the current version of TalkTalk Mail.  It's therefore up to the sending mail service to improve their reputation by eliminating spam at source.

What's the originator's email domain? Is it a personal email domain sometimes known as a vanity domain? If so, which mail service is hosting that domain?

The 'sometimes' gets the bounceback error message is interesting. Sometimes can be because blacklisting often does auto-expire after two weeks. Or sometimes is because the sender of the mail is relaying via another mail service that doesn't rewrite the header and therefore TalkTalk will be inspecting the source SPF file and if that does not allow relaying then may be treating it as potential spam.  

Your answer(s) to the email domain / hosting may reveal the answer.