Help with SPF - @ symbol in email address being replaced with "40"!

Server Config
1

Hi,

I’ve got a domain with SPF configured on it. It’s been working fine for some time. However, recently sent emails are being rejected by various mailservers. It seems they are interpreting the sender address “user@domain.com” as “user40domain.com”. This means that although there is a correct SPF record for “domain.com” it thinks the domain name is “user40domain.com” and then finds the SPF record to be missing / invalid.

The SPF records we have set up for the domain are:

spf2.0/pra mx include:_spf.zen.co.uk -all
v=spf1 mx include:_spf.zen.co.uk -all

Does anyone have any ideas why some mailservers are interpreting the @ symbol as 40 and then finding the domain name invalid?

Thanks

Ben

2

40 is the hex value for @

Are you trying to send the email address in the URL?

3

No, the SPF record only holds the domain name.

99% of all mails that are sent are accepted by the receiving mailserver. It’s just a small proportion are being rejected. It could be that the recipient mailservers are configured incorrectly and are using the sender’s email address to do the SPF lookup (after substituting the hex value for the @ symbol) instead of just the domain name…

Any further thoughts?

Thanks

4

Sorry - misphrased my reply just now. We’re not sending any URL - just the email headers contain the sender email address - recipient mailservers should do a DNS lookup on the domain, get the SPF records, and then validate the sending mailserver according to the SPF rules. However, the mailservers that are bouncing the messages seem to be using the user40domain.com to do the SPF lookup rather than just domain.com…