email funny

The email server thinks your trying to 'relay' through it. In the good old days, an email server would happily accept a message from (for example) snipped-for-privacy@somedomain.com and deliver it to snipped-for-privacy@anotherdomain.com without checking the sending or receiving domains at all. And then someone invented spam. So now, email servers check to make sure that either the sending domain, or the receiving domain, is the same as the domain they were setup to cater for. If neither match the server's own domain, then you are considered by be 'relaying' through it, and very few servers will allow that these days. In fact, ones that do will usually find themselves on a blacklist.

Having said all that, I still can't say exactly what's wrong, but I hope you have some idea of what the email server thinks is going on. Most likely is that your sending account is configured with an email address that the server is not configured to be a host for. It doesn't normally matter what the receiving email address is, because otherwise no-one would be able to send email to anyone :-)

It looks like you are sending through a plusnet SMTP server. They will only accept un authenticated SMTP requests from users with an IP that is inside one of their net blocks. If you attempt to connect from an external IP, then you also need to authenticate to demonstrate you are one of their legitimate users.

Which email client are you using?

I would suggest you look what the email client now requires and set your SMTP setting accordingly for the email domain address.

It does suggest they are clamping down on their server being used for spam. Not a bad thing.

which this would seem to be (171.146.112.87.dyn.plus.net)

True, but he hasn't/isn't I suspect that plusnet has added some net blocks and not told their smtp relay about them yet.

The connection is via a plusnet web connection, not a plusnet mail server The same problem is happening with other servers in other countries, makes me think it's our US based mail server provider changing the software. This is on outgoing mail only.

email across the domain works. ie snipped-for-privacy@capitol.org to snipped-for-privacy@capitol.org.

Does the provider provide SMTP submission port 587 (or perhaps legacy

Yup, fair point - I just looked at the IP and did not recognise it as one of their normal netblocks.

Sounds plausible...

Also some SMTP servers are getting more touchy about the types of connection that they will accept - many only accepting encrypted connections now. (although not the case in this circumstance looking at the error)

Er no, it isn't.

Explain please.

The five mail servers I use all only allow encrypted connections and its a good thing IMO.

Even my own, which I don't currently use, is configured for encrypted only.

That is not a message rejecting mail from a web server, but from the users own PC.(87.112.146.171 is router,192.168.0.5 is PC itself)

Generally yes, unless you need to maintain email working on a legacy platform that does not have modern email clients.

Not that dennis' opinion is worth squat, but you put in an email proxy.

Although I expect you know that ...