Email scheduler for Gmail - check duplicate draft

Overview blog post.

The following Google Apps Script code takes the message ID from the getDraftMessages function and checks to see if a corresponding value already exists within the spreadsheet. This is likely to occur as a user runs to import their draft messages multiple times over the course of using the tool before they have all been sent. So this way we can avoid them seeing the same entry multiple times.

The script simply looks down the Message ID column (via 'getRange' and 'getValues'), then loops through each row looking for an ID match. It uses a duplicateFlag variable set to false by default, to signal a duplication (becomes true) and then stops the script from continuing to run via a return command.

This in turn then allows the parent function to behave appropriately and not import the duplicate draft message. If everything is fine and no duplicate is found then the flag remains false.