[k-9-mail] Poll IMAP or delayed fetch

[Christopher]

I'm using an external anti-spam system that checks my IMAP account and
moves SPAM to a SPAM folder.
It's working fine, but when a message is received on my account, it is
first received on K-9 (playing the "incoming message sound") and then moved
to the SPAM folder (the external anti spam filter takes some milliseconds
to process the message).
Since I don't want to hear the incoming message sound for messages that are
then moved to the SPAM folder, I would like to setup a small delay in K-9
so the messages are processed by the anti spam filter before being received
on K-9.
Can this be accomplished using poll instead of push for IMAP?
Or is there any configuration to introduce a small delay when fetching
messages?