DNS - SPF records - Gmail Alias Help

We have a domain [login to view URL] who receives mail to a Merak Mail server. Some accounts such as sales@[login to view URL] are forwarded to a Gmail account mygmailaddress@[login to view URL] that is setup to be able to send mail as an alias for sales@mydomain.com. Recently we are getting deliverable messages saying: (see below) ## Deliverables Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 Your sender is not permitted (read [[login to view URL]][1]) (state 18). ----- Original message ----- Received: by [login to view URL] with SMTP id n9mr2431939yao.23.<wbr />1320058756428; Mon, 31 Oct 2011 03:59:16 -0700 (PDT) MIME-Version: 1.0 Sender: [mygmailaddress@[login to view URL]][2]Received: by [login to view URL] with HTTP; Mon, 31 Oct 2011 03:58:34 -0700 (PDT) In-Reply-To: <<wbr />9AC38CB902524359B914629F4BE2A6<wbr />E4@UserPC> References: <<wbr />3C60BB65AD6943028842824538BDC3<wbr />20@UserPC> <<wbr />839E7625DCE649DB92FC678DF7EC4B<wbr />88@UserPC> <<wbr />247918F3333341999AFA50CB60D804<wbr />9E@UserPC> <<wbr />9AC38CB902524359B914629F4BE2A6<wbr />E4@UserPC> From: "[sales@[login to view URL]][3]" Date: Mon, 31 Oct 2011 06:58:34 -0400 X-Google-Sender-Auth: TJp7xRXKWcnWmzukRwExOGs0SBw Message-ID: Subject: Re: Dealer To: Ivan Woon Content-Type: multipart/alternative; boundary=<wbr />000e0cd3989242746404b09621ff Hello Ivan, (generated by Pobox::Web::Controller::<wbr />External) I emailed them and they said "Domains with questions about SPF should go to the SPF Forums at [://[login to view URL]<wbr />[login to view URL]][4] We use Simple DNS on a Windows 2003 server and Merak Mail server on a separate server.