What is not considered a “source” in Google Analytics by default?
“Email” is not considered as a source in Google Analytics. “Email” comes under the “Medium”.
In Google Analytics, “Source” is the origin of your traffic. For example, search engines, referral websites (domains). Note the difference between sources and mediums. Mediums are categories of the sources, for example, organic search (organic), cost-per-click paid search (cpc), web referral (referral).
So, in this case, email is not a source in Google Analytics.
Analyzing your website traffic sources can help marketers understand how well campaigns are working and how to optimize website content, advertising, and other marketing channels.
Learn more on the official Google support website.