computer help: hi, i use gmail as my email. - Help.com

Deleted is not destroyed.
But to make it readable again you need to bring your mac to a specialist — and it will be VERY expensive to scan the whole disk for deleted files!
Beside that: If it had happened over a year ago, the chance is very small to locate the deleted files. It depends on the load capacity of the disk. If it is high then perhaps the files were overwritten since then.

Well.. If you used Gmail and it’s web based frontend, deleted items end up in the Trash Can (Gmail’s, not your computer’s). However, they are automatically deleted after 30 days and can’t be recovered.

If you used a Mail Client in your computer to retrieve emails from Gmail (instead of the web-based alternative they offer), things are a little different. If your mail client was accessing Gmail using IMAP, it is basically the same as using Gmail’s web based frontend, the mails were never downloaded to your computer and they are basically gone. If your mail client was accessing Gmail using POP, it did download the emails from gmail to your computer.

However, although it IS usually possible to recover deleted files from the computer, it is a very expensive process when done by a specialist (thousands of dollars) and the files are only recoverable if their physical location on the hard drive was never overwritten. After a year, forget about it. The chance you can recover any of those emails is astronomically small.

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TL;DR - Forget about the emails, they are permanently gone.