Apple Mail on Mac Computer error

Mac Apple mail error.

When I start Apple mail on my Mac computer an empty new email composition appears over the top of the default mail program.

I have to close the new blank email to view the main mail screen.

If I minimise the mail program and than click the mail icon to maximise and view the mail program the same thing happens.

How can I stop this? I just want the default program to open, not a new empty email composition as well.

Anyone able to help?

Thanks.