Test your SPF record online:
Running spfcheck.pl from 18.104.22.168
If we sent you a Non-Delivery Report (NDR), you can send an email (*) to the special test address given in the NDR.
When you send a message to that address, our server will automatically test your SPF record and reject the message with another NDR. The NDR will contain the results of the tests on your SPF record.
The reply will explain any issue (or issues) found, and what can be done about it (or them).
Normally it does not matter what you put in the test message, it will be ignored. But if the original NDR we sent was not sent to the address that you're now going to send your mail from (that is you're going to send a test message to us from a different address this time), then in your message you need to tell us the address that the NDR was sent to. Otherwise we won't know what's happening. Just put the original address anywhere in the message body, our server will find it.
* Unfortunately there are people Out There who like nothing better than to get in everybody's way by sending millions of pointless messages.
So we have to take precautions, to protect ourselves (and everyone else).
Our servers will not reject the first mail to the address in the NDR. But the address is for use once only. Subsequently, mail to that address will be rejected.