Gmail accounts come with 15GB free storage. In the beginning, it seemed impossible to use that much space. After a decade of saving everything, including receipts, family vacation planning threads, coupon codes for stores you don't shop at, love letters and so on, you will soon reach that limit. It is time to delete.
My Gmail account was set up in 2007 and I haven't been very organized. It is difficult to get rid of almost 15 years worth of emails. I do my best to unsubscribe when it becomes too overwhelming.
It is easy to mass delete Gmail messages. Type Label:all mail in the top search bar and hit enter. You will see options directly below the search bar. These include the ability to select emails from a particular sender, a time period, and messages with attachments. I am guilty of subscribing and letting accumulate newsletters without opening them. I use mass-deleting from the sender, but attachments can take up too much space. (chain emails dating back to 2008, we hardly knew you).
After you have selected your filter method, click the checkbox in the upper left corner of the message list to make sure all messages are selected. Click Select all conversations matching this search to delete more messages than 50. Click the trash icon.
Gmail keeps all deleted emails for 30 days if you decide to change your mind. To delete these emails immediately, you can click on the checkbox at the top of your trash folder and click Select all conversations matching this search. Click Delete forever. RIP.