iCloud & iCloud Photos · Messages, Mail and device backups in iCloud
Does iCloud Mail count toward my iCloud storage?
Short answer: Yes — iCloud Mail messages and attachments, including Sent and Trash, count toward iCloud storage, and a full iCloud can stop new mail arriving. Delete large emails and empty the account's Trash to free space.
Yes. Emails and attachments in your iCloud Mail account — including Sent and Trash — count toward your iCloud storage. When iCloud is full, iCloud Mail may stop receiving new mail.
To free space, delete large emails and old attachments, then empty the Trash mailbox for that account. Sorting by size in Mail helps find the biggest ones — see finding the biggest emails in Mail. Mail stored on the Mac uses Mac space separately.