Even though there are some Email App alternatives in the macOS, the Apple Mail App is still the most used for Email. If you have several Email accounts like I do, then you may have difficulty keeping them straight in the Mac Mail App. Here is a suggestion that might help to work with your Email.
I do not have all of my Email accounts setup in the Mail App right now. I have several Gmail accounts along with some iCloud ones. If you do have several accounts in your Mail App, they will be listed in the left sidebar.
In this case, I only have the iCloud account showing, but most of the time I have four or five different accounts listed there.
A simple solution for differentiating and keeping these accounts straight is to give them individual, recognizable “Descriptions”. That is done in the Mail Preferences Account Tab.
When you set up an Email account in the Mail App, a generic account description is provided. It is helpful to click in that field and provide a more informative description for that particular account.
Just provide whatever description enables you to quickly identify that account. Whatever the purpose of the entity is, name the account accordingly.
The account Description is a very minor setting in the Mail App, but personalizing it can make things a little easier in dealing with your Email workflow.