Mac storage basics · Mail, Messages and chat apps
Does removing an email account from my Mac free up space?
Short answer: Yes — it removes Mail's local copy. Server-based accounts keep their mail online; export local-only mailboxes first because they may be the only copy.
Yes, for the copy on your Mac. Mail keeps a local copy of each account's messages and attachments. Removing the account (or turning off Mail for it in System Settings → Internet Accounts) deletes that local copy and frees the space.
For most accounts the messages stay on the email provider's server, so you can add the account again later and they download again. If an account only exists on your Mac — such as an old POP account or On My Mac mailboxes — export what you need first, because removing it can remove the only copy.