Sender Policy Framework (SPF) is an open standard that senders can use to publish which IPs are authorized to send email from their domain. If your mail server has an SPF check that blocks emails that fail SPF, this can cause delivery problems for senders that use SPF because email is delivered to your mail server from SpamHero's IPs.
If SpamHero detects a bounce caused by an SPF filter on the receiving server, it will automatically re-deliver the message using a technique that bypasses the SPF filter. TLDR
For those that want to know, the technique is pretty simple... when an SPF bounce is detected, the message is re-sent to your mail server after modifying the return path to use our server's host name (the "From:" is not touched).
Despite this feature, we still recommend utilizing one of the solutions below which prevents the sender from receiving a bounce or for situations where there is no bounce and the receiving server silently fails to deliver the message due to an SPF issue.
Any of the following solutions can be used to resolve SPF delivery problems:
A common mistake we have seen our customers make is to delete their domain's own SPF record in an effort to shut off the SPF filter for their mail server. There is no reason to delete your domain's SPF record as that will have no affect on your incoming email. Your domain's SPF record affects your outbound email only.