topic Re: Sudden SPF failures in Email

Sudden SPF failures

softhedgehog — Tue, 04 Feb 2025 12:31:13 GMT

I have an SPF record in the service that I use to send email. It looks like this (and has done so for ages):

v=spf1 a mx include:_spf-internal.plus.net include:_spf-internal2.plus.net include:soverin.net ~all

I have had few problems sending until suddenly this morning I am getting failures like:

host 10.93.165.123 [10.93.165.123]
    SMTP error from remote mail server after pipelined end of data:
    550-SPF failed: <domain name> is not authorized by SPF (SPF Result:
    550 softfail)

Can anyone enlighten me?

Re: Sudden SPF failures

Townman — Tue, 04 Feb 2025 12:37:46 GMT

The first thought which comes to mind is who are you sending to? (Email domain)

Do you know if the email address you are sending to is the final delivery address?

In a situation where...

You send an email to fred@freds-domain.co.uk
Which is directed to fred@freds-mailprovider.co.uk
And freds-domain.co.uk does not support SRS

Then freds-mailprovider.co.uk will see an email as being sent from you by freds-domain.co.uk mail server ... which does not match the SPF rules.

So the question to be explored, is this occurring with just one email address or many?

Re: Sudden SPF failures

softhedgehog — Tue, 04 Feb 2025 14:21:12 GMT

It is a group email address that I have been using for as long as I remember. Last successfully used on 28 Jan (a week ago). One of the addresses on the list is mine and that is bouncing! Nearly all the email addresses on the list are included in the bounce - that one shows that the final address is showing there (which is the PlusNet address).

Re: Sudden SPF failures

Townman — Tue, 04 Feb 2025 15:15:31 GMT

OK, looking back at this ...

10.93.165.123

Is a private network ... which makes me wonder where the SPF bound message came from.

You need to break down into micro detail what you are trying to do and how things are configured.

Are you sending from you@youraccount.plus.com
Or from you@yourdomain.co.uk
1. Is that domain hosted by Plusnet
2. Or a third party - who
Whose SMTP server are you sending through
The email address in the list which is yours - is that your
1. Plusnet address delivered to a Plusnet mailbox
2. Plusnet address forwarded to some other address
Can you try sending to each address (actually domain) individually to determine which remote system is belly aching

On rereading I note the soft fail status . under the rules, a soft fail should be delivered, but marked as potential spam.

Is one of Gmail, Outlook, Hotmail or live.co.uk involved in this issue?

Re: Sudden SPF failures

softhedgehog — Tue, 04 Feb 2025 16:10:20 GMT

I am sending via relay.plus.net. The From address on the email is another domain name, which is hosted by Heart Internet.

If I send an individual message, it seems to disappear without trace - not even a bounce.

I have just sent a message to my plusnet account directly and that has arrived, but I am not sure that even left the plusnet servers. I have sent another which definitely goes out of plusnet and that has now arrived (an earlier one did not).

I am very confused.

Re: Sudden SPF failures

Townman — Tue, 04 Feb 2025 16:42:35 GMT

Revisiting your SPF record, it has include:soverin.net ~all tagged on the end of the recommended Plusnet list - why if you only send via Plusnet's relay server?

Also when running the above through a SPF checker, it reports back as...

v=spf1 ip4:185.233.34.0/24 ip6:2a10:de80::/32 -all

Note the minus-all which is a firm fail as opposed to ~all which is a softfail - I wonder if that is causing confusion?

Re: Sudden SPF failures

softhedgehog — Tue, 04 Feb 2025 17:16:58 GMT

Everything seems fine again. I haven't changed anything, so it must have been a glitch somewhere else.