Create mailbox functionalities without using in-built mailbox

SystemVerilog
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1

One of my colleague has been asked with this question in an interview recently.
How can we create a mailbox with using in_built mailbox?
If you can add code as well, it will be helpful

2

In reply to bachan21:
https://verificationacademy.com/forums/systemverilog/question-internals-mailbox-built-class#reply-53565