SquirrelMail

In SquirrelMail 'None' is special keyword and can't be used as mailbox
name.

sqimap_mailbox_select() function does not select mailbox.

displayPageHeader() function does not display 'Current folder: None' in top
menu bar.

In 1.4.9cvs right_main.php does not display messages in None mailbox.

In 1.5.2cvs right_main.php creates PHP notices, because
sqm_api_mailbox_select() expects array with IMAP SELECT command data and
sqimap_mailbox_select() returns NULL.

You already have FIXME tag in 1.5.2cvs functions/imap_mailbox.php.

PHP notices can be reproduced only on servers that have empty string as
personal namespace prefix. dovecot 0.99, hmailserver, mercury32 and other
simple IMAP servers without namespace support are affected. cyrus and
courier are not affected. uw is affected only when uw preset is not used.

If displayPageHeader() is fixed, it will break backwards compatibility and
all plugins that depend on $mailbox='None' must be updated. If empty string
is used instead of 'None', updated plugins are backwards compatible with
older SquirrelMail versions.