IMAP / Delayed Notification of New Mail

I have seen similar problems reported several times on these forums, but the problem still seems to persist.

I am accessing my Zoho account through IMAP (specifically using Mutt and Thunderbird), and have noticed that, when a mail is sent to my account (from a different account), it will take a long time for my mail client to be notificed (even when refreshing the client and/or logging in and out from Zoho (in the client).

For the mail to come through immediately, i have to log into the Zoho website, or (if i'm already logged in) refresh the Zoho webpage. After doing this, my IMAP client will be able to pick up the new mail immediately. This is annoying behaviour.