Net:POP3 and Mailbox problem

I'm trying to pick up messages from my account and save them in my Mailbox on
machine, where exist no MTA.
Net::POP3 can connect me to server, read messages and save them in file. What's
a problem? I'd like to use mutt and read these messages. But mutt complains:
Mailbox is not Mailbox(Mailbox is file where i saved what i retrieved ).

snippet follows:
---beg---
open ( MAILBOX,">>/root/Mailbox");
for my $msgnum (1..$numberOfmess){
    
     my $content= $minv->get($msgnum);
    print MAILBOX join "", @$content;
    
}
close MAILBOX;
exit;
---end---

Can somebody tell me, what's wrong with my Mailbox? Messages are there, only
mutt refuses to read them.

    ico66
Please answer me directly to [email protected], i'm not subscriber. 
Simple reply won't work.