Google Analytics reads referring site information to try to classify incoming traffic for its reporting, but referrers can be misleading. For example, when clicking on a link in a marketing email, the referrer may be reported as Comcast or Hotmail, when it’s source was really an internal email campaign. For this reason, it’s best to always tag all email and paid traffic links, to tell Analytics to ignore the referrer, and use the information you’ve embedded in the URL instead.
Analytics provides a simple URL Builder tool for tagging your URLs. For AdWords PPC traffic, Google can automatically append identifying tags your PPC links. In AdWords, go to My account, Preferences, Tracking, Auto-tagging and select yes. For all other paid traffic and emails, including Bing Ads, Facebook and others, you’ll have to manually generate tagged links using the Google URL Builder.
Once your entire team is properly tagging links, you’ll be able to use the rich feature set throughout Google Analytics with clarity. Your channels will be reported correctly, and you’ll have separate reporting buckets for your various traffic driving efforts. This segmentation will allow deeper inspection of the individual traffic sources, as well as its overlapping action occurring in your Multi-Channel Funnels area of Analytics.