Most email clients these days offer the ability to utilize the IDLE function of IMAP. What the IMAP IDLE function does is leave a connection open on the mail server, then as soon as a new email has arrived it alerts the mail client and pushes the new message to the client.
In theory this sounds like a good thing to have configured for your mailbox, unfortunately we've seen many problems with the way that Apple's Mac Mail handles this function of the IMAP protocol. Often times it leaves open multiple IMAP connections instead of just one and over time they can pile up and can eventually get you blocked from the server. The reason for this is that in a shared server environment, we must limit the amount of concurrent imap connections that can be made from a single ip address. If you have a small office where everyone is using Mac Mail and then compound that with tablets and smartphones, you can understand how the connections can pile up. This is not a concern for our clients using dedicated offerings, but for shared hosting users it is important for us to limit these connections.
If you're using Mac Mail and have multiple email accounts on the same server or you are in an office environment, you should disable the IMAP IDLE function. To do this, follow the steps below:
1. From the Mail dropdown, click on Preferences.
2. Click on Accounts.
3. Select your imap account from the list on the left.
4. Click on the Advanced tab.
5. Disable the Use Idle setting.
