How to set up Mail on macOS Sequoia with two synced iCloud accounts and Gmail

Having two iCloud accounts (your personal one and your work one, or an old @me.com and a new one) plus a Gmail account on the same Mac is more common than you might think. And while it sounds trivial, as soon as you add three mailboxes to Mail at once, problems start to show up: passwords that aren’t accepted, duplicate folders, notifications firing three times over.

This guide takes you from zero to a working setup on macOS Sequoia 15.x with the Mail app that comes with the system. Estimated time: 15–20 minutes if you have your passwords and verification codes handy.

What you’ll get with this setup

You’ll have all three accounts living together in Mail without clashing: two independent iCloud accounts (with their own calendars and contacts if you want) and a Gmail account via IMAP with OAuth. Everything with unified mailboxes so you can read incoming mail from all three in a single inbox, while still being able to reply from the correct address.

You’ll also see how to avoid the classic problem: Mail duplicating the Gmail “Sent” folder because it doesn’t recognize Google’s labels.

Prerequisites

• macOS Sequoia 15.1 or later (the guide works the same on 15.2 and 15.3).
• The Mail 17.x app (the one that ships with the system, nothing needs to be installed).
• Access to both iCloud accounts with their passwords and, if you have two-factor authentication enabled (you should), a trusted device nearby to receive the code.
• A Gmail account with two-step verification enabled. If you don’t have it enabled, turn it on first at myaccount.google.com.
• 15–20 minutes and some patience for the first Gmail sync if you have a lot of email.

Adding the first iCloud account

If you already have an iCloud account linked to the Mac (the one you use for the system Apple ID), this part is already done. Check it in System Settings → [Your name] → iCloud → Mail. If the toggle is on, your @icloud.com email is already in Mail.

If not, or if the Mac is shared by several people and you’re not signed in with that account:

1. Open Mail.
2. Go to the Mail → Add Account menu (or from System Settings → Internet Accounts → Add Account).
3. Select iCloud.
4. Enter the Apple ID and password.
5. If you have 2FA, enter the verification code sent to your iPhone or iPad.
6. Check Mail in the list of services (you can also enable Contacts, Calendars and Notes if you want).

When it’s done, a section with that account’s name and its mailboxes (Inbox, Sent, Trash, etc.) will appear in Mail’s sidebar.

Adding the second iCloud account

This is where many people get stuck. macOS assumes you have a single primary Apple ID, but it lets you add additional iCloud accounts for mail only.

1. Go to System Settings → Internet Accounts.
2. Click Add Account at the bottom.
3. Choose iCloud.
4. Enter the second Apple ID (the other iCloud account) and its password.
5. Verify with the 2FA code.

Important: here macOS will only let you enable Mail, Notes and Find My for this second account. Contacts and Calendars remain tied to the system’s primary Apple ID. This is a limitation of macOS Sequoia, not a mistake on your part.

If the system complains with “Identity could not be verified”, close Settings, wait a minute and try again. Sometimes Apple is just slow to propagate the second sign-in.

App-specific passwords (if the normal method fails)

If for some reason the second iCloud fails to link (this sometimes happens with old @me.com or @mac.com accounts), generate an app-specific password:

1. Sign in to appleid.apple.com with the second account.
2. Go to Sign-In and Security → App-Specific Passwords → Generate Password.
3. Give it a name (e.g. “Mail Mac work”).
4. Use that 16-character password instead of the real one in the Mail setup step.

Adding the Gmail account via IMAP

Gmail in Mail works with OAuth 2.0, not with a direct password. This is good: you don’t enter your Google password on the Mac, and if you revoke access from Google, it’s cut off cleanly.

1. In Mail, go to the Mail → Add Account menu.
2. Select Google.
3. A browser window (or a Mail pop-up) will open with the Google login.
4. Enter your @gmail.com address and password.
5. Confirm the second factor (SMS code, phone prompt, physical key, whatever you use).
6. On the permissions screen, review what Google is asking for (read, send, manage) and click Allow.
7. Back in Mail, choose which services to sync: Mail is essential, Contacts and Calendars are optional.

If instead of OAuth you get a form asking for the password directly, Google has detected something unusual or your account is old. In that case, enable Less secure app access from your Google account (not recommended) or, better yet, generate an app password from Google’s security settings and use it in Mail.

Setting up unified mailboxes

With all three accounts added, Mail’s sidebar becomes a mess: three “Inbox” folders, three “Sent”, three “Trash”. Unified mailboxes group them into a single view.

1. In Mail, click the button to show the sidebar if you don’t have it visible (⌘ + Shift + M toggles the mailbox list).
2. In the sidebar, hover over the Mailboxes section and a + button will appear, or use the Mailbox → New Smart Mailbox menu in the top bar.
3. For a true unified view, simply drag the “Inbox” folders from all three accounts into a common folder, or better yet: click the small triangle/arrow next to Inbox in the sidebar and Mail will show the three mailboxes grouped below the unified “Inbox” it already creates by default.

By default, Mail already gives you a unified “Inbox” at the top of the sidebar that combines all three accounts. The same goes for Sent, Trash and Drafts. If you don’t see it, go to Mailbox → Show All Mailboxes or check View → Customize Toolbar.

Choosing the default sending account

With three accounts, when you press ⌘ + N to compose a new email, Mail will pick one by default. To change it:

1. Mail → Settings → Composing.
2. Under Send new messages from, choose the default account or leave Account of currently selected mailbox (recommended: it sends from the account of the mailbox you’re reading in).

On each new email, at the top, there’s a From: dropdown to change the sending account on the fly.

Avoiding the duplicate Gmail “Sent” folder

This is the classic problem: you send an email from Gmail in Mail and it appears both in Gmail’s “Sent” and tagged with the [Gmail]/Sent label. It’s fixed in two steps:

1. Select the [Gmail]/Sent folder in Mail’s sidebar (inside your Gmail account).
2. Go to the Mailbox → Use This Mailbox For → Sent menu.

Repeat the same with Trash, Drafts and Junk if you see duplicates. You’re telling Mail: “this Google-labeled folder is the real one, don’t create a parallel one”.

Common problems and how to fix them

“The Gmail account keeps asking for my password every 5 minutes”
It’s an expired OAuth token. Go to System Settings → Internet Accounts → [your Gmail] and click Delete Account. Add it again from scratch. The token will be regenerated.

“The second iCloud account shows as offline in Mail”
Check at appleid.apple.com that the account isn’t locked after failed attempts. If everything is fine, in Mail go to Mailbox → Connect All Accounts or press ⌥ + ⌘ + L.

“Mail keeps downloading Gmail messages forever”
The first sync of a Gmail account with a large history can take hours. In Mail → Settings → Accounts → [your Gmail] → Mailbox Behaviors, check whether downloading complete attachments is enabled. To speed things up, go to Advanced and limit sync to the folders you use.

“I get triple notifications for the same email”
This usually happens if you have Gmail also synced through iCloud (forwarding) or if email is forwarded between accounts. In Mail → Settings → Rules you can filter duplicates. Also in System Settings → Notifications → Mail you can leave alerts for only one account.

“I can’t move emails between accounts”
You can, but dragging from one iCloud to Gmail (or vice versa) means uploading the entire message to the other server. With heavy attachments this takes a while. Be patient, or use Message → Forward as Attachment if you just want to archive it somewhere else.

FAQ

Can I have three iCloud accounts in Mail at the same time?
Yes. macOS Sequoia lets you add multiple iCloud accounts as additional “Internet Accounts”. Only the first one (the system Apple ID) has all services; the others are limited to Mail, Notes and Find My.

Is it worth using Mail instead of Spark, Airmail or Gmail’s web interface?
It depends. Mail integrates natively with Focus, Handoff, system notifications and Spotlight. Spark has better productivity features (snoozing, templates). Gmail’s web interface has the most powerful filters. For managing two iCloud accounts + Gmail without paying a subscription and with full macOS integration, Mail does the job.

Do Gmail emails take up space on my Mac?
Yes, Mail caches emails locally in ~/Library/Mail/. With a Gmail account that’s several years old it can take up several GB. If you’re short on disk space, limit the folders it syncs from Mail → Settings → Accounts → Gmail → Mailbox Behaviors.

Can I use the same setup on iPhone and iPad?
Yes, on iOS 18 and iPadOS 18 the process is practically identical from Settings → Mail → Accounts → Add Account. Accounts don’t sync automatically between Mac and iPhone; you have to add them on each device. The exception is if you use iCloud Keychain, which at least fills in the passwords for you.

And if I want to unify the contacts and calendars of both iCloud accounts?
You can’t do that from the system. macOS only associates Contacts and Calendars with the iCloud of the primary Apple ID. If you need the contacts from the second account, open icloud.com in your browser, export the contacts as vCard and import them into the Contacts app on your Mac.