GMail Email delivery Failure issues

Good day,

I have two separate domains with email services through Homestead.

www.brownspecialtyparts.com

www.mechengineering.com

with both of my main email addresses:

sbbrown@brownspecialtyparts.com

sbbrown@mechengineering.com

I cannot send email to any GMail address and potentially any other email domain that does not accept unauthenticated emails.

I get this error:

 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 [brownspecialtyparts.com] with ip:
    [66.96.184.2] = did not pass

Can you assist with this issue or advise what is needed on my end?

I am sending and receiving mail through Outlook on my desktop.

Can you also post a reply to either of my email addresses?