I understand how to apply Outlook rules to Gmail when filtering incoming messages but I have not found any similar support for rules on outgoing messages. The way I set up my Outlook account was to have a rule where all my outgoing messages are delayed by one minute (sit in my outbox for one minute) before actually being sent. The reason for this is to avoid double emails. I'm sure we've all sent an email only to realize we forgot to include the attachment seconds later.
Is there a way to set this up for Gmail?
Best Answer
Gmail filters act on incoming messages, not outgoing. (Gmail support: Using filters).
However, you can ameliorate those "oh no" moments by turning on the "Undo Send" lab in Gmail Labs.
Gmail Blog: New in Labs: Undo Send
Essentially, this "holds" a message for up to 30 seconds to give you a changes to hit "Undo" and pull it back before it's truly gone.
Further, Gmail is pretty smart and can tell that you probably meant to include an attachment and will alert you if you forget. (Here's the announcement of the Forgotten Attachment lab, but it has since graduated from the labs and is now a built-in feature.