Is it possible to trace an email address?

You can get a lot of information from the header. It will tell you the the originating IP address and will lead you to a block of numbers belonging to the internet provider. Law enforcement can ask the provider who belongs to a specific number.

There are ways to spoof and trick the system. Crooks and scammers do it all the time.

So if it isn’t the email address isn’t the main one, can it be traced to the main one?

Not from the printed email !
The information of where it came from is in the “header” and “source” code available from a drop down window on the email ( on the computer). The real senders address is the “postmark” or cancellation, not the return address” on the envelope, The return address can be added just like putting address label from a self sticking sheet of addresses.

@Tropical_Willie is correct as far as he goes.

However, it is trivial (incredibly simple) to fake and spoof those headers. So don’t trust them to be corrrect.

Unless the printed email has the header info included it will not be useful. Often the IP address will give you a general area of where the email originated. You can tell if it came from someone’s mail server at work or if they did it from home using a local provider.
The header info can be spoofed or anonymized, but most people don’t know how to do it and in general is correct.

Yes, it is possible. Someone might need access to the computer that received it.

She only has the printed copy. The email address is clear on it. She said her brothers friend can trace this to the sender. She mentioned some kind of m r number. She knows about as much as I do with computers, nothing. Does she know what she is talking about here?