Provider guide · iCloud Mail
Apple lets third-party apps into iCloud Mail on one condition: an app-specific password, created from your Apple Account with two-factor authentication on. Create it first; the settings themselves are the standard three fields.
1 · Credentials
Your Apple Account password never goes into a third-party app. Apple’s substitute is the app-specific password, and creating one requires two-factor authentication on the account.
In Sign-In and Security, select App-Specific Passwords.
Choose Generate an app-specific password, name it, “WordPress” for instance, and copy the result straight into the plugin.
An account can hold up to 25 of these, one per app, revocable one by one from the same screen. And a warning that saves a future debugging session: changing your Apple Account password revokes every app-specific password at once, WordPress included.
2 · In the plugin
Selecting the iCloud preset fills the server (smtp.mail.me.com), the port (587) and the encryption (TLS). What remains is yours.
The full iCloud address, you@icloud.com, not the short name. Apple is explicit that SMTP wants the whole address, even though its IMAP settings often use the short form.
The app-specific password, not your Apple Account password.
The same iCloud address.
Save, then use Send Test Email, and check the log row it produces either way; iCloud’s error sentences are short but honest.
3 · Pitfalls
iCloud Mail is a personal mailbox with personal-mailbox rules; the pitfalls follow from that.
Reset your Apple Account password and every app-specific password is revoked on the spot. The site starts logging authentication failures with no other change anywhere. The fix is routine once known: generate a new app-specific password and paste it into the plugin.
iCloud Mail allows up to 1,000 messages and 1,000 recipients per day, at most 500 recipients per message, and Apple states plainly that the service is meant for personal use, with bulk sending against the rules. A small site’s notifications fit; a growing store should look at a transactional provider such as Brevo or Amazon SES.
iCloud Mail counts against your iCloud storage, and a full quota blocks sending and receiving alike. If sends start failing while the credentials have not changed, and especially if your inbox has gone quiet too, check the storage before anything else.
The email log keeps the exact error message the server returned, which is the fastest route to the cause. The documentation walks through the common ones.
There is a guide like this one for each of the twelve presets, from Gmail to Amazon SES, and the plugin takes any other SMTP server too.