iCloud email won’t send? Here’s what to check to fix it

Email may seem quaint to some people, but billions upon billions of messages are sent that way every day. (Some we even want to receive!) Apple’s iCloud service includes an email address and the ability to send and receive email. But you may occasionally be stymied in sending a message without enough of a detailed error message to know why iCloud rejected it.

Here are the most common reasons:

• Invalid iCloud address: Apple can’t check whether an email address is legitimate at other domains, but if you try to send email to someone with an address that ends with icloud.com, mac.com, or me.com, and that address doesn’t exist, your email app and iCloud.com will refuse to send it. Your app may not tell you which address is incorrect, too, requiring sleuthing on your part. (Invalid addresses at other domains will be rejected by those domain’s mail servers in the form of an email message in reply.)
• Too many recipients in one message: It’s likely rare that you’re sending a message to a vast number of people, but Apple does limit your recipients to a total of 500 per message.
• Too many recipients across all messages: You’re also limited to 1,000 recipients across a 24-hour period and 1,000 email messages total. Recipients don’t have to be unique—that is, people will be counted multiple times across different messages. If you send 10 messages each to 100 people, 100 messages each to 10 people, or 1,000 messages to one very exhausted person, it counts the same.
• Attachment size exceeded: The text and attachments combined of an email message sent or received can’t exceed the absurdly small amount of 20MB. As I type this, I find that hard to believe in 2021, but it’s what Apple’s documentation says. You can enable Mail Drop in Apple Mail, which uses iCloud for temporary storage for attachments totalling up to 5GB per message. Mail Drop has its own set of limits.

This Mac 911 article is in response to a question submitted by Macworld reader Linda.

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