Is there a way of tagging/flagging PMs in the inbox as "Important" or "Do not delete"?

I wanted to put a marker on the messages which had addresses of those who wanted to be Guinea Pigs but I couldn't find a way of doing it.

I'll ask Kestrel 

Ta.

Hello Elaine,
If you go to your messages,

Then in Preferences menu, choose Manage Labels.
Then create your Label name.

Then back to messages.

You can the apply the label you created to any message you select.

Basically, the label appears to act like a folder.
By labeling a message, it copies from the inbox to the label name.

I tried and once the label is applied, you can apply other labels to the message and the message will appear under those labels as well.

So labeling appears to be somewhere between tagging and copying the message.

I should add, that if you want to "un-label" a message, don't delete the message...just apply the label again to the message.

Thanks - got them sorted now.