The Mail Merges section in the left-hand Gmail menu lets you access all of your mail merges to find their current status and performance, or to take action on your mail merges.
In the My Mail Merges list, find:
all of your mail merges and their current status
how many recipients have been added to each mail merge
number of emails send, viewed, and replied to
when the most recent email in the mail merge was sent
when the first email in the mail merge was sent
You can also choose to see only your active mail merges, or all of your drafts in the left-hand Mail Merges menu.
Click on a mail merge in the My Mail Merges list to see the status of the message for each recipient. You can also pause or resume mail merges or messages to individual recipients from this page.