VM Moderation: What Does the Message "This Message is Moderated" Mean?

[Saitama]

I just noticed that the VM i receive or are sent by me have a message on them "This Message is Moderated". What's this? I don't think i have done any wrong recently that my VMs need to be moderated.

 

[Greg Bernhardt]

To combat some spam, we've moderated all VMs. You did nothing wrong. Should be accepted very shortly :)