Many of us use third-party apps which need to connect to services provided through our Apple ID. In my case, one of the most important is Postbox, the email client which I use in preference to Apple’s Mail. The other day, it reported that it couldn’t connect to Apple’s IMAP server to synchronise, and prompted me to try again or supply a new password. When I checked with Apple’s System Status, I discovered that iCloud Mail was having a bad day, so cancelled further error dialogs from Postbox.

My problem persisted, eventually leading me to make a common mistake. Having become so used to entering my regular Apple ID password, I tried using that to let Postbox connect to Apple’s IMAP service. It didn’t work, so I fiddled a bit more with the account settings without success.

I had forgotten an important rule which applies to all third-party apps which connect to services provided through your Apple ID: they aren’t allowed to authenticate using your regular Apple ID password, but have to use specially-generated app-specific passwords instead.

If you’re having trouble getting a third-party mail client to connect with Apple’s IMAP service, this support article steps you through the settings and points out the need for an app-specific password. If you’ve forgotten a previously-generated password or want to create a new one, this article explains how to do those.

Sign into your Apple ID account page and look at its Security section.

For the full service, click on the Edit button here.

You can then generate a new app-specific password, or list those which you’ve already created.

You can revoke any or all existing app-specific passwords, as you need.

In my case, all I did was create a new one, enter that into Postbox when it prompted yet again for the IMAP server password, and everything was fixed again.

Remember the rule: you should never have to enter your regular Apple ID password into a third-party app, but use an app-specific password instead.