emails bounce between forwarders

[#1]

I have two forwarding email address, mine (roger@...) and my wife's (helen@...) each set up to point correctly to plusnet servers (mail...., relay...) All been working fine for 10 years. Suddenly, a month ago, emails sent to ourselves or each other have started bouncing back, mostly at least - around 20% do arrive. All other emails to/from other people arrive to/from these forwarding addresses as usual, just ones we send to ourselves or each other. Not the fault of the PCs, it happens if we send something to us from phone or tablet. And, oddly, occasionally, such emails just disappear into the ether, no rejection!

The bounce back message is:

Diagnostic-Code: smtp; 550 5.7.1 Message contains spam or virus. (110) [1643033874-743657] DMARC policy violation.

(I have no automatic spam intercept, and use Norton anti-virus)

I have raised this with my domain provider who tried but, basically, couldn't fathom out why this is happening and suggested I contact Plusnet (will Plusnet pass me straight back!) It is really annoying, and nobody seems to have an idea what is causing this and why it has suddenly started happening after 10 years! 

Any thoughts would be very welcome, but in simple language please - I'm no techie!

Thanks all

[#2]

Do you have an SPF record for your domain ? and does your forwarding support SRS ( Sender Rewrite system ) ?

[#3]

Hi Superuser - thank you for your response, I'm very grateful to you for taking the time

I did warn you - I have no idea what a SPF record is, nor whether my domain has a SRS (domain is with UK2.net if it helps). I have had quite a correspondence with UK2, they tried various things, so I imaging they have looked at what you suggest. But I could go back to them and ask about these things.

Again, if such things exist, it is puzzling why this has only given trouble recently

Again, thanks

Regards

Roger

[#4]

Sorry, I missed the last line in your original post. SPF is used to define which email servers are authorised to send mail for a domain. See https://en.m.wikipedia.org/wiki/Sender_Policy_Framework .

The problem when email is forwarded, is that the email is effectively being sent by the forwarding server and not the originating one, and thus is not on the list of authorised servers.,SRS allows,a forwarding server to rewritevemail headers such that the email appears to come from the originating server and so still meets any SPF requirements. Problem is that many forwarding systems don't do SRS properly.

The reason it may only just be happening is that more and more email receiving servers are using SPF to control receipt of mail and spam detection.

I'm afraid that given the amount of spam around these days, if you have a domain used for email then you need to be aware of SPF,DKIM and if you forward email the SRS as well.

[#5]

Thank you Superuser, what you say makes sense and suggests, basically, that I may need to change my domain provider? Presumably nothing I can request from my domain provider? Or anything else I can do?

Thank you again

Roger

[#6]

You could ask uk2 to confirm if they support SRS when forwarding emails.

You could use one of the domain lookup tools like https://mxtoolbox.com/ . Do a basic mx lookup and then use the drop down box to select spf lookup to see if you have an spf record and what it defines as authorised servers

[#7]

The most straight forward solution is to avoid forwarding all together.  Host your email service on the MX for the domain name or point the domain name to a host MX service.  Domain name sellers with just email forwarding such as UK2 have the risk of steering you into messes such as this.

There are numerous mail hosting providers which are not overly expensive - less than £2 pcm.

[#8]

Thank you MisterW, Townman, I shall look into all this tomorrow

Regards

Roger