Recommended way to pause postfix local delivery while taking snapshot for backup

[Dominic Raferd]

Is there a best/recommended way to pause postfix local deliveries so that I
can take an LVM snapshot of the local mails for backup purposes? The pause
only has to be momentary, while the snapshot is taken, but the files need
to be in a consistent state. If anyone also knows the way to pause Dovecot
imap/pop3 similarly (as this could also be accessing the same files), that
would be helpful too.