I can give you another "hint" to help you along the way...If you're attempting to get an item that wasn't sent to you, then you're in for a BIG surprise, because without modifying the database directly there wouldn't be a way to do that.
I think it would be in your best interest to know that the method you're trying to use is probably the worst one out of all the mail commands.
Also, another piece of information...
Typical format for databases on in game mailing systems are set up like this...
Username
subject
body
gold
item
Vindictus is a little bit different, and as such is set up different.
Just remember that vidnictus has two types of mail, most games don't.
This means that Subject, Username, and Body text go into the regular letter, which has an ID that correlates with the Item_mail's id in a flag in the database, this is how they call on each other to link into one message (ever notice when someone sends you an item it says 2 MESSAGES, not one.)
You need to be able to link the messages, find out the correlating ID's, then find out the correct syntax for item get, and you'll be a LOT closer than you are for right now.
As for how to do that, well, that's where database knowledge, and php scripting come into play, and considering that I've never heard anyone else talk of things such as this I don't think many people here share the level of expertise that i do in that field

But, to those of you that do, Nexon doesn't allow their queries to come straight into their servers, they use services provided by amazon to synch the information from their server to amazons, so you've got two levels of hacking to go through, added to the level of ASPX and in game cookie hacking that you'll have to perform in order to get this working
Again...good luck to all of you, it's not NEAR as easy as you think it is.