There is a rule in the US government that all officials should use their official email, rather than personal email.
This rule seems to apply also to many commercial companies. I presume that the purpose is to allow the organization to check on what the employee is doing. But why is it necessary?
Many government agencies and commercial companies in Singapore also follows this practice.
I find this rule to be inappropriate. I use my personal email address for personal and business purpose. Instead of talking to someone over the telephone, I send an email. Why should I have to use the official email address?
If it comes to a business deal when a record is required, we will probably use a signed document anyway, and send by PDF.