I have had several e-mails to one of my long-standing trusted clients bounced back with this message:
An interesting bounceback. The recipient does check for spam and it does this in two ways. Checking spam blocklists and checking the incoming email for acceptable authentication.
The smtp server is listed on Sorbs Spam blocklist. However, the server isn't responding normally so may have been taken offline.
As for authentication you would get the best chance of getting email accepted if using secure ports, getting network authentication and having the return address the same as the sending address.
Thanks for your help. I was just checking through the settings and the problem seems to have cleared, so it may, as you suggested, have been that a server was temporarily off-line.
...Good to know that normal sending and receiving is ok.
Just for clarification I was talking about the talktalk smtp outgoing server not responding as normal. I don't think there is anything particular wrong with the recipient's server but the recipient's host does have a 'zero tolerance for spam' type of message on the server response.
I don't know if this is related to the same problem, but since Friday sent e-mails have either not been arriving or arriving up to 12 hours after they were sent. I can't tell whether it is just to one recipient or others. I've not received any mailer-daemon messages, just e-mails vanishing.
Hi Artistef, there's been a backlog of mail that needs clearing since the incident. I suspect that will be causing the delays to your mail.
Back after a week away and the Senderscore problem is happening again, same domain, different recipient, and as before the blocked IP's are not listed as blocked by Senderscore.