Sentbox Vs Outbox in PHPBB

Hi I'm new to forum magement and I would like to know what's the diff between the sentbox and the outbox in phpbb. I PM 2 users in my forum and one msg in sentbox and one in outbox. Does it meant tha the msg in outbox is not sent out? If so, what should i do?

Thanks for your help.

 

if it's in sentbox, it's been opened and read by teh recipient

if it's in the outbox, recipient just hasn't opened it yet- nothing you need to do differently

 

Thanks for your explanation.. I've never know that.. hahah

 

I was also wondering thanks rep added.