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Setting Up ActiveSync on iPhone, Android, and Outlook

Exchange ActiveSync (EAS) is the protocol that synchronizes email, calendar, contacts, and tasks in real time with mobile devices and desktop clients. Zimbra hosted at InteSys supports ActiveSync natively on the Business plan — no plugins, no manual IMAP setup.

Why ActiveSync Instead of IMAP?

Feature IMAP + CalDAV ActiveSync
Email Yes Yes
Calendar Via separate CalDAV Built in
Contacts Via separate CardDAV Built in
Real-time push With IDLE Yes, native
Folders and subfolders Yes Yes
Synced read flags Yes Yes
Remote wipe No Yes
Setup 3 accounts (IMAP + CalDAV + CardDAV) 1 account

For business users, ActiveSync is the simplest and most complete way to access Zimbra from mobile devices or Outlook.

Business Email Only

ActiveSync is available only on the Business Email plan (Zimbra). The Professional plan supports IMAP/SMTP + CalDAV/CardDAV.

Connection Details

Before configuring any client, note the following:

Setting Value
Server mail.yourdomain.com (or mail.intesys.io)
Domain (leave blank)
Username Full email address
Password Your email password
SSL/TLS Required (port 443)

iPhone and iPad (iOS 15+)

  1. Settings > Mail > Accounts > Add Account
  2. Choose Microsoft Exchange
  3. Fill in:
  4. Tap Next > Set up manually
  5. Enter your password
  6. Under Server, enter: mail.yourdomain.com
  7. Leave Domain blank
  8. Tap Next
  9. Choose what to sync: Mail, Contacts, Calendars, Reminders, Notes
  10. Tap Save

The initial sync starts within seconds. Default history: 1 week of email — adjust it in Settings > Mail > Account > Mail Days to Sync.

Android (Samsung, Google Mail, Outlook)

Gmail / Google Mail

  1. Gmail > Menu (≡) > Settings > Add account
  2. Choose Exchange and Office 365
  3. Enter your full email address > Next
  4. Enter your password
  5. Under Server settings, enter:
    • Server: mail.yourdomain.com
    • Port: 443
    • Security type: SSL/TLS
  6. Next > accept the device policy > Done

Samsung Email (preinstalled on Galaxy)

  1. Open Samsung Email > Add account > Other
  2. Enter your email and password > Manual setup > Microsoft Exchange ActiveSync
  3. Server: mail.yourdomain.com / Domain: blank / SSL on
  4. Next > finish

Microsoft Outlook for Android

  1. Open Outlook > Settings > Add email account
  2. Enter the email address > Continue
  3. If autodiscover does not identify it, choose Exchange manually
  4. Server: mail.yourdomain.com / leave domain blank
  5. Sign in

Outlook Desktop (Windows and macOS)

Outlook 2016 and later support ActiveSync. For Zimbra accounts over EAS:

Windows

  1. Control Panel > Mail (Microsoft Outlook) > Email Accounts > New
  2. Choose Manual setup > Outlook.com or Exchange ActiveSync compatible service
  3. Fill in:
    • Name: your name
    • Email address: full address
    • Server: mail.yourdomain.com
    • Username: full email address
    • Password: your password
  4. Next — Outlook validates and finishes the setup

macOS

  1. Mail > Settings > Accounts > +
  2. Exchange > Enter your name and email > Sign in
  3. Under Set up manually:
    • Internal/External server: mail.yourdomain.com
    • Domain: blank
  4. Choose what to sync (Mail, Contacts, Calendars, Notes, Reminders)

New Outlook (2024+)

The "new Outlook" for Windows has limited EAS support for non-Microsoft providers. If you run into issues, switch to classic Outlook (available from the same toggle) or set up IMAP + CalDAV as an alternative — see Calendar and Contacts.

Troubleshooting

401 Error (Invalid Credentials)

  • Confirm the username is your full email address, not just the local part.
  • Clear the Domain field — Zimbra does not use an NT domain.
  • Check whether the password was changed recently (the first login after account creation requires a password change in webmail).

403 Error (Forbidden)

  • Does your plan include ActiveSync? Only the Business plan does.
  • Has the device policy blocked the client? The admin can view registered devices in the panel and approve them manually.

Invalid Certificate / SSL

  • The correct server is mail.yourdomain.com with a valid certificate. If the autodiscover CNAME has not been configured yet, use mail.intesys.io temporarily (the certificate is compatible).
  • See the DNS Configuration Guide to configure autodiscover.yourdomain.com.

Sync Loop

  • Did it start after a password change? Remove and re-add the account — ActiveSync does not recover expired tokens.
  • Mailbox very large (> 10 GB)? The first sync can take several hours; wait it out or reduce the sync history to 1 month.

External Diagnostics

To separate configuration issues from network or server issues, use the ActiveSync Test — a free InteSys tool that simulates an EAS connection and pinpoints exactly where it fails (authentication, protocol version, folder discovery).

Learn more about the Zimbra Business Email plans — all include native ActiveSync with no per-device license fees.