I just found a question tagged bot, google-mail (x2) and gmail (x198). Does that really make sense? One could argue the former is for the service, while the latter is for the app. Wrong: Both questions tagged 'google-mail' are about the app (GMail app setup, install google apps).
Thinking about it: All our google apps tags tart with
google-[maps|talk|voice|calendar|plus|...]. So a tag like
google-mail makes absolutely sense to me, and would count as "consolidation". Hence my suggestion:
Merge the two making
google-mail the master and
gmail a synonym to it. There's not a lot of tag wiki for either of them (just an excerpt on
gmail which could easily be cut'n'paste (for Germans: Guttenberg-Schavant ;)).