When you open a Gmail message, you often see ads related to that email, Google is now rolling out improved algorithms to more relevant and unobtrusive ads in Gmail. “From now on, you’ll sometimes see ads matched to another recent email instead. For e.g., you’re looking at a message from a friend wishing you a happy birthday. If there aren’t any good ads for birthdays, you might see Chicago flight ads related to your last email instead. To show these ads, our systems don’t need to store any extra information — Gmail just picks a different recent email to match. The process is entirely automated: no humans are involved in selecting ads, and no email or personal information is shared with advertisers,” explain Gmail blog.