From 6.3.10:
"the STATUS command SHOULD NOT be used on the currently selected mailbox."
but in theory, the use of STATUS to ask if new mail has arrived is also
not legal:
"The STATUS command MUST NOT be used as a "check for new
messages in the selected mailbox" operation (refer to
sections 7, 7.3.1, and 7.3.2 for more information about
the proper method for new message checking)."
6.3.10. STATUS Command
Arguments: mailbox name
status data item names
Responses: untagged responses: STATUS
Result: OK - status completed
NO - status failure: no status for that name
BAD - command unknown or arguments invalid
The STATUS command requests the status of the indicated mailbox.
It does not change the currently selected mailbox, nor does it
affect the state of any messages in the queried mailbox (in
particular, STATUS MUST NOT cause messages to lose the \Recent
flag).
The STATUS command provides an alternative to opening a second
IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
query that mailbox's status without deselecting the current
mailbox in the first IMAP4rev1 connection.
Unlike the LIST command, the STATUS command is not guaranteed to
be fast in its response. Under certain circumstances, it can be
quite slow. In some implementations, the server is obliged to
open the mailbox read-only internally to obtain certain status
information. Also unlike the LIST command, the STATUS command
does not accept wildcards.
Note: The STATUS command is intended to access the
status of mailboxes other than the currently selected
mailbox. Because the STATUS command can cause the
mailbox to be opened internally, and because this
information is available by other means on the selected
mailbox, the STATUS command SHOULD NOT be used on the
currently selected mailbox.
The STATUS command MUST NOT be used as a "check for new
messages in the selected mailbox" operation (refer to
sections 7, 7.3.1, and 7.3.2 for more information about
the proper method for new message checking).
Because the STATUS command is not guaranteed to be fast
in its results, clients SHOULD NOT expect to be able to
issue many consecutive STATUS commands and obtain
reasonable performance.
