Lots of people have pointed out several possible improvements to this feature. Now if we could anticipate these things with a few minutes of contemplation (each), I'm sure Google would have come up with the same list of gripes.<p>But obviously, they did some tradeoff analysis and decided to do what they did.<p>Now, from a technical standpoint, the fact that they implemented this feature in the present way results in <i>some</i> information of their internal infrastructure and engineering organization to leak through.<p>The 5 second, non-configurable timeout should allow us to speculate a little bit on what Gmail's architecture is.<p>The only reason I can think of is that maybe the undo operation results in a scan over <i>all</i> queued email for all users. This is obviously an expensive operation, so maybe they cannot easily increase this delay with their current architecture. They'll have to add per-user queues on their servers. Maybe that's too big an engineering project at present.<p>What do you think?<p>Microsoft Outlook has had a sophisticated version of this for a long time. I know a guy who had set up Outlook to send <i>all</i> his email 30 min after he hit send. You can even schedule a message for sending at an arbitrary time (i.e., per-message level granularity of send delay).<p>For instance, the Microsoft Outlook implementation of this feature essentially implies that each client can queue up emails for later delivery on the server and <i>later</i> interrogate this queue in a sophisticated way (i.e., it's not fire and forget).