how do i remove my Apple mail and reinstall Apple Mail on an imac computer

You cannot, Mail is part of Mac OS therefore the app cannot be "uninstalled" or "removed". If your system needs to be updated, please update it.

What is the problem you are experiencing that makes you want to uninstall and then re-install Mail?

That isn't a reason to uninstall Mail. Read the mail, the ones you don't want Trash them. If you get mail from a source you no longer want to receive mail from then create a rule. Use rules to manage your inbox will help you create rules.

Mail appears to be corrupted. When I compose an email and press the send button, the email is deposited into an outbox folder that I've never used before. It can't be mailed from the outbox and instead the window displaying the message repeatedly vanishes and reappears. Nothing can be done to stop that vanishing/reappearing except dragging the email from the outbox folder back to the drafts folder. Trying to send the email again simply reinitiates all the nonsense. How do I reinstall the OS?

Once I have some information on the model year and version of Mac OS currently installed on your Mac I can provide information about re-installing Mac OS. You can find this information by clicking the Apple symbol in the upper left of the display and then selecting About this Mac.

However before moving forward with a re-install of Mac OS. PLEASE ensure you have a complete backup of your computer. You need a Time Machine backup or a bootable clone of your system. This simply to protect your data in the event something goes wrong.

Can you post a screenshot and maybe we can help.