ERROR_CODE :550, ERROR_CODE :5.1.0 74.201.84.163 is not allowed to send from <mydomain.com> per it's SPF Record

ERROR_CODE :550, ERROR_CODE :5.1.0 74.201.84.163 is not allowed to send from <mydomain.com> per it's SPF Record

I am experiencing trouble. My mails are not being delivered and this is the failure message that I get. Please i Need urgent help! 

This message was created automatically by mail delivery software.
 A message that you sent could not be delivered to one or more of its recipients. This is a permanent error.

mycustomer@customer.com, ERROR_CODE :550, ERROR_CODE :5.1.0 74.201.84.163 is not allowed to send from <mydomain.com> per it's SPF Record. Please inspect your SPF settings, and try again. IB508  <http://x.co/srbounce>


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        with SMTPS id 1463839980258497. 53933321695285; Sat, 21 May 2016 07:13:00 -0700 (PDT)
 Message-ID:<CAKykb3GiZY1pvDJF= YC1RLxUURt0FFf9-ZbM= 4hPYSpXXyQUpg@mail.gmail.com >
 Date:Sat, 21 May 2016 09:12:59 -0500
 From:me 
To: Customer
 Subject:Prueba
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