Recipient address rejected: Message rejected due to: SPF fail - not authorized

Question

I company wants to send email to us, but it gets bounced back with the error

"Your message wasn't delivered due to a permission or security issue. It may have been rejected by a moderator, the address may only accept email from certain senders, or another restriction may be preventing delivery. Recipient address rejected: Message rejected due to: SPF fail - not authorized."

I've checked our records and theirs in https://mxtoolbox.com and get no obvious errors. Now I'm stuck. Any advice as to what else to check?

Solution

Within their company's DNS, they have willingly specified that their emails are sent using email provider A, whilst sending their emails using email provider B. Your own mail provider sees this and immediately thinks that the email is not legit, because of their own DNS policy (this is called the SPF Record).

You may: 1) Tell them to update their DNS SPF record so that their mail server is authorized (they can do some research). 2) Check your own mail provider settings to see if there is an option to allow any emails coming from their server IP or their domain.