basic question about relational databases

[danicgross danicgross]

Hi -

I'm currently designing a messaging system for a website.
The current outline I have is this:
table: USER_KEYS
-uid //user id
-incoming_keys //FK's for all messages user has, references to PK in "incoming"
-outgoing_keys //FK's for all messages user has, references to PK in "outgoing"

incoming table:
-mid //message id, auto increment
-text //message text
-of course other things like read/unread ect..

same for outgoing.

my question is - firstly, am i doing this right?
second - if i am, can i have multiple foreign keys in one field? For example:
uid: 4, incoming_keys: 2021, 503, 34243, 2340.
will mysql recognize this?

thanks.