gmail ads targeting
How the GMail ads targeting work?
For keyword targeting - Do Google scan the subject line of the emails that an user receive or scans the content of the email to match with the keyword list?
Interest - This seem too broad to perform efficiently, isn't it?
Re: gmail ads targeting
Keyword targeting in Gmail Ads works by matching the keywords you want to target to a user's inbox. It will scan a number of factors, including subject line and content, to try to match your ads to the most relevant users. These keywords are broad match by design. You can also layer different targeting options like keywords + interests like you would in a typical display campaign, by choosing the Target & Bid option.
Hope this helps!