Gmail blocking emails from homestead-hosted domains.

Google has starting blocking emails that don't meet their authentication requirements. This is causing serious problems for me because many of the folks who I normally communicate with use gmail addresses. Please give this some attention soon. I've pasted one of the Mail Delivery system responses below:

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

    host gmail-smtp-in.l.google.com [142.251.167.27]

    SMTP error from remote mail server after end of data:

    550-5.7.26 Your email has been blocked because the sender is unauthenticated.

    550-5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM.

    550-5.7.26

    550-5.7.26  Authentication results:

    550-5.7.26  DKIM = did not pass

    550-5.7.26  SPF [stellarwoods.com] with ip: [65.254.253.86] = did not pass

    550-5.7.26

    550-5.7.26  For instructions on setting up authentication, go to

    550 5.7.26  https://support.google.com/mail/answer/81126#authentication d75a77b69052e-494ae40cb0esi202983591cf.85 - gsmtp