If you think oxwall is going to help you with a custom modification to your site like that your pissing in the wind. 

Keep in mind that the documentation oxwall is extremely lacking, so local devs are your best bet.

Good luck.

Don't you think that you're looking at the matter from the wrong angle?

Even if there was a way to enter user mailboxes, what if you have more users, you will spend all your site management time on deleting those scam messages from their inboxes

I believe you should look at this post first: http://www.oxwall.org/forum/topic/11284

What you want to achieve is considered as a custom paid plugin development, as Phil mentioned we do not provide assistance with such service , you need to hire a programmer to do that for you, you can do that here: http://www.oxwall.org/market/specialists

I believe there's a misunderstanding here!

My message is pretty clear straight forward, if you look at point 2: I said to delete all message from certain users. So there's no search for messages on the system as you have mentioned.

Highlighted points:

1- Admin access users mailboxes

2- Admin delete all messages from certain user (messages should be delete from the SENDER and RECEIVERS inboxes)

Steps are easy and clean: admin click on user name from admin area AS USUAL, then the admin click on user's MAILBOX then delete all the messages.

Pretty simple , isn't it ?

Thanks 

Unofortunately there's no such functional in the default software. 

There's a plugin called "Login as a user" which you can take advantage of, but even if you use this plugin, you can delete the message on the RECEIVER end only, unless you go to the senders account via this plugin and delete it from there as well.

I know you mentioned that we should not suggest you obtain a plugin, but in the meantime, I believe this is the only option for you to enter other users mailboxes to delete messages, or you should do that via phpmyadmin or you need to develop a separate plugin

Can you please explain on how to block certain countries within oxwall itself as I have other websites running on my hosting account and I don't wish to block them from cPanel to be able accessing my other websites.

Edit: I already have  Login as a user but it doesn't do what I want 

There's no such functionality in the default software as well. 

However you can block the IP range from the CPanel, there should be a feature called IP blockerI recommend you to check this post: http://www.oxwall.org/forum/topic/11064