how do you empty/delete trash,,does it free up memory?

Memory = RAM = Random Access Memory. The more applications and processing that are running at one time, the more Memory is used.

The Less Applications running at the same time, the less RAM is used.

The above is totally normal and how RAM works.

As Others have already mentioned - Internal Drive Space and Drive Capacity is a totally different matter and is independent from RAM Usages in this specific case E-Mails

bettina133 wrote:

does emptying email trash free up memory?

If by "memory", you mean storage space, yes. But, unless you have lots of large attachments, probably not by very much. Emails are very small files.

Understand, we are all working Remotely from all around the world. 

Therefore, we do not have the On-Hands experience the User ( you ) has with this computer.

The next best thing for us to having a semi - actual On-Hand experience on this computer is to follow the steps below

Download the Application Etrecheck directly from a well Respected ASC Contributor. And Safe to use.

The application is free or paid from added features. 

Run the application with Full Disc Access ( Security & Privacy - Full Disc Access ).

It will take a Snap Shot -  both the hardware and software.

 The Report will Not Reveal Any Personal Information. 

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.

Yes of course, emails received in mac mail will gets stored in your device, this will occupy some space.

Yes of course, but kindly keep in mind that this will also delete in cloud storage too like Gmail, outlook, etc.,