We're expecting some inclement weather tomorrow and we would like to be able to send to our students an email stating that we are cancelling classes for the day should we have to close the campus. We have an "allstaff" distribution list set up with all of our users in it and when testing this out (we've just now gotten around to actually using this) I get the following error:

Out: 220 myserver.com ESMTP Postfix
In: EHLO myserver.com
Out: 250-myserver.com
Out: 250-PIPELINING
Out: 250-SIZE 42048000
Out: 250-VRFY
Out: 250-ETRN
Out: 250-STARTTLS
Out: 250 8BITMIME
In: MAIL FROM:<admin@myserver.com>
Out: 250 Ok
In: RCPT TO:<allstaff@myserver.com>
Out: 250 Ok
In: DATA
Out: 354 End data with <CR><LF>.<CR><LF>
Out: 451 Error: queue file write error
In: QUIT
Out: 221 Bye


Help!!