as you all realized that many posts did lost its attachment(s) after board updates, so may I suggest a mass PM to be sent to all MSFN members regarding this issue, and to gently asked members to review their posts to upload attachments in case it was lost

Unfortunately, you can't send so many PMs. And each post will not necessarily get its attachment sent again.
We'll probably have to wait for something from IPS.

What is the IPS

Invision Power Services.

I used to be a member in some forums websites, and was one of staff team, and I was able to use and find this feature to send a PM for all members, does MSFN using another tool that does not allow such a thing

It all depends on the forum software.

Thanks