A picture?

Impossible to answer without at least seeing a picture illustrating the door and its interface with the box. An explanation of how it is supposed to catch or latch would help, too.

Would appreciate any suggestions
Buy a better mailbox?

leave it open

With donation envelopes.

It should be fairly simple to find and install a magnetic catch.

Photos would help. How was the door closure accomplished originally and what has changed and how has it changed?

I have 4 different types of welding equipment in my shop and can mend almost everything except a broken heart and the crack of Dawn. Someone in your area has similar capabilities.

Thanks all for the replies. Unable to send picture and I purchased a mailnut which is a magnet and it worked for 6 months so perhaps welding is the answer. Volvo