Forum Moderators: Robert Charlton & goodroi
Why don't you pose that question to Google and see what they say.
Or in the altenative make up a page about some unknown phrase, put it in a directory with other pages but with no inbound links to it.
Then send your gmail account some emails containing a link to that page and see what happens.
And second, think about it - the last thing Google wants to do is to invite a flood of yet more spam, spam that isn't pitching viagra for a change but instead backlinks. Counting backlinks that appears in gmail would be a open invitation to a flood of spam from desperate webmasters trying improve their backlink counts.
And they also say, in the Gmail Terms of Use, that they "will not use any of your content for any purpose except to provide you with the Service."
It seems very unlikely to me that they'd use links that could be found in emails in any way in search rankings. Not only would the value of doing so be questionable in terms of improving quality of the results, but technologically it wouldn't fit into most of the established approaches (taking into consideration patents, publicly released documents, and the canon of IR techniques) that it can be safely assumed they do use. How would email content fit into the web map? Since there are no incoming links to email documents, how could they be assigned a PageRank? Or an authority score? Etc., etc.