Use a combination of the Select tool and the Trash button in Gmail to delete multiple messages simultaneously. Deleted items are sent to your Trash bin and remain there for 30 days before Gmail deletes them completely. You can recover deleted messages from the Trash at any time during this 30-day period.
Step 1: Locate and filter the messages you want to delete. Use the Search tool to search for messages by email address or keywords.
Step 2: Select the messages you want to delete. Place check marks next to individual messages or click the Select button and choose All to select all items that match your search criteria.
Step 3: Click the Trash button to move the selected messages to the Trash.
Mass-Deleting Starred and Un-starred Messages
To delete starred messages only, click Starred on the left of the main Gmail screen. Alternatively, click the Select menu and choose Starred. You can also use the Select menu to choose un-starred messages.
Recovering Messages From the Trash
You have 30 days to recover deleted messages from the Trash. To view the contents of the Trash, hover your mouse over the label list located under the Compose button on the left of Gmail, click More and then select Trash.
Select the messages you want to recover from the Trash, click the Move To icon, which resembles a file folder, and select Inbox to move the messages back to your Inbox. You can also move recovered items to other locations. [ref 1]