How to delete duplicate files on Mac Pro?

The biggest files in stored email inBox tend to be pictures attached to emails.

If you sort your emails by SIZE, you can find the biggest boat-anchors quickly.

as etresoft suggests, moving those emails to a folder located under the "on My Mac' heading will store them in your local computer, freeing up storage space on the email server.

here is more discussion on the subject of space:

How to free up ‘System Data’ and other st… - Apple Community

JoyceLittell wrote:

My MacPro is running out of storage. I keep deleting spam, etc. but have many duplicate files. Is there a way to search for and delete duplicates without having to do so manually?

Searching for and deleting duplicates would probably be a waste of your time. Most duplicate files actually don't take up any additional storage. They're clones.

JoyceLittell wrote:

Google One says - You're out of storage and will stop getting emails, starting on Jan 5.

Get more storage with a discounted plan $16.99 for one year and then $19.99 for following year. Sounds like Google One needs more money to build more data centers. What's the solution? Switch to Yahoo?

That sounds like some kind of online cloud storage plan. Maybe you just need to delete e-mail messages.

If you have an Apple Account, then you can use that for e-mail. And if you use Apple Mail, then you can save your e-mail messages to your local machine instead of keeping them in the cloud.

JoyceLittell wrote:

My MacPro is running out of storage. I keep deleting spam, etc. but have many duplicate files. Is there a way to search for and delete duplicates without having to do so manually?

I don't get it... are you saying this is a Mail.app issue?

Control click on your Mail account> Get Account info

You will get a big picture look for that account...