emails by gmail marked as suspicious

Our wordpress site running Woocommerce and hosted on Nexcess/Liquidweb, is having issues sending emails generated by woocommerce or our Contact Form 7 plugin. The messages are being sent via our gmail account to recipients and are marked with RED question mark (?) that says the message is suspicious and often sent to spam folders. We know that wordpress used the PHPmailer function for email. Is there an easy code snippett or plugin that will setup Google SMTP servers and can anyone provide guidance on how to setup SPF record and DKIM records within our Hosting DNS environment?