Spam is very complex issue, but most cases can be resolved by implementing SPF and DKIM. Sender Policy Framework and DomainKeys Identified Mail can help verify your emails are not modified and sent from approved server.
You can´t control how recipient server will evaluate your message, but having properly configured SPF and DKIM is a good start.
- do not use Spam filters to whitelist external domains or users. In some scenarios this could help to pass phishing email through Google filters
- regardless of the Spam filter settings, google may put incoming email into a spam folder
If you are still experiencing difficulties don't hesitate to contact us here.
Support team Revolgy