You mean open the mailbox anywhere?
There's cc_mailbox_ui but i never really used it...
I think it works even on a boat. I don't really think you could accept a mail without opening the mailbox, because it would require to specify which mail you want to use and all.
But since you can open the mailbox anywhere... It's pretty much the same. Btw there's a post not far with all the console commands... You should look at it.