message undeliverable from own domain to talktalk email accounts

[oldfogie]

I'm sending emails out from my own account (eg "fake@mydomain.org.uk") to a group of people.

I'm getting "message undeliverable" when I try to send to talktalk email accounts -

and also to one tiscali account - but its working fine to gmail, yahoo mail, and others.

Also working fine to my own domain eg "john@mydomain.org.uk"

The emails have a suitable subject and content so spam filtering etc should not be an issue.

I've tried several times with the same results. Can you help please?

[Gondola]

You've PM'd the domain to me so I have looked up the SPF file. There is an SPF file but I do have a concern that it offers no security to your domain because it allows any sender to pass authentication. Your domain could easily be spoofed. The last entry on the SPF file is + All and it would be better with - All as the last entry to restrict sending to the permitted servers only.

The domain IP address is on the s5h.net blacklist because spam has hit spam traps. I'd say this is the reason for TalkTalk rejecting the inbound mail.

You can request a manual delisting. However, when I check the relevant website I'm getting a report that Malwarebytes has detected a trojan on the s5h.net (redirected) site. I'm therefore concerned that effecting a remedy may not be itself without risks. Do keep your security defences fully updated and active.

[Gondola]

Do you have your DNS name server set up with an SPF text file (Sender Policy Framework) to authenticate the sending of your personal domain mail? If I knew the domain I could check for you. PM me the domain if you wish.

TalkTalk are likely to reject any mail that is not authenticated with SPF and does not use DKIM signing or have a DMARC policy.