I once worked for a company that after a merger had a bank account running just to pay services it didn't know what they were for.

If you grow, have a merger, people moving, it is easy for email addresses to no longer be read. Yes there are best practices to prevent this, but most companies I have seen don't do that.

In one company important emails wen to the email address (external!) of the founder, who lefter after M&A.