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GMail authentication bounces

You receive a confusing bounce message like this

Remote Server returned: '550 5.7.26 This mail has been blocked because the sender is unauthenticated. 5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM. 5.7.26 5.7.26 Authentication results: 5.7.26 DKIM = did not pass 5.7.26 SPF [site.com] with ip: [204.140.21.15] = did not pass 5.7.26 5.7.26 To mitigate this issue, please visit Gmail's authentication guide 5.7.26 for instructions on setting up authentication: 5.7.26 https://support.google.com/mail/answer/81126#authentication i10-20020a63bf4a000000b005ab6142f1besi2075781pgo.169 - gsmtp'

All domains hosted here have always had a default SPF record set up, that covers at least 95% of use cases,  But despite Google stating that either SPF or DKIM is required, it seems they will now fail a message with SPF only, even if it is valid.  Therefore you also need DKIM.

On the Windows Server side this isn't something you can manage yourself through the Plesk control panel as your mail server is on a remote networked machine.  So you'll need to open a support ticket in the client area and request we set up DKIM for you.  We are happy to help with that, it just takes a few minutes and Google will then be satisfied that your outgoing mail is authentic.

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