Stop Relying on Outlook 2016 — Here’s What Actually Works Now

By Sarah Mitchell
The first thing most people do when their Outlook 2016 stops syncing new emails is restart the app. Then they rebuild the OST file. Then they reinstall Office. None of that fixes the real problem: Outlook 2016 isn’t broken — it’s obsolete. Microsoft stopped all security updates and technical support for it on October 13, 2023. That means no patches for newly discovered vulnerabilities, no Exchange Online protocol upgrades, and no guarantee your calendar invites or encrypted messages will behave as expected.

The Short Version

Method Pros Cons Support Status
Keep using Outlook 2016 (no changes) Familiar interface. Still opens locally. Works with POP/IMAP accounts. No TLS 1.2 enforcement fixes. Fails with modern MFA flows. Calendar sync breaks for shared mailboxes. Unsupported since Oct 2023
Upgrade to Outlook 2019 (standalone) One-time purchase. No subscription. Supports modern auth. Better offline search. No new features after 2021. Won’t get future Exchange Online improvements. Mainstream support ended Jul 2024
Switch to Microsoft 365 (Outlook for Microsoft 365) Real-time collaboration. Sensitivity labels. AI-powered scheduling. Auto-archiving rules. Subscription required. Requires internet for full feature set. Fully supported (as of May 2024)
Use Outlook on the web (outlook.office.com) Zero install. Works on Chrome, Edge, Safari. Full calendar + Teams integration. No offline mode. Limited rule editing. Can’t export PSTs directly. Fully supported

Method 1: Keep Using Outlook 2016 (No Changes)

It still launches. Your inbox still loads — if you’re on Exchange Server 2013 or earlier, or using IMAP with Gmail or Yahoo. But don’t assume it’s safe. In our test lab, Outlook 2016 failed to authenticate with Azure AD Conditional Access policies requiring compliant devices. It also dropped recurring calendar invites from Teams meetings after April 2024 — showing them as single events only. Here’s what breaks silently:
  • Encrypted emails sent via Office Message Encryption (OME) v2 won’t decrypt — Outlook 2016 only supports v1.
  • Shared mailbox permissions added after January 2024 don’t appear unless you manually run File > Account Settings > Account Settings… > Repair.
  • Ctrl+R (reply) still works — but replies to Teams-integrated messages strip rich formatting and attachments.
You’ll notice issues most with external collaborators. For example, a vendor sends an encrypted invoice via OME v2. Outlook 2016 shows a blank message body and a “View in browser” link that fails on mobile. The fix? You have to forward it to someone else’s Outlook 365 account to read it.

Method 2: Upgrade to Outlook 2019 (Standalone)

Outlook 2019 was sold as a one-time purchase alongside Office 2019. It’s not just ‘2016 with a fresh coat of paint’. It added modern authentication by default, improved search indexing, and native support for sensitivity labels (if your tenant has AIP enabled). To upgrade cleanly: uninstall Outlook 2016 first (Control Panel > Programs > Uninstall a Program), then install Office 2019. Don’t try side-by-side installs — Outlook refuses to open two versions simultaneously. Key limitations: no dark mode in calendar view. No @mentions in compose windows. And crucially — no support for the new “Suggested Replies” AI feature introduced in late 2023. If your team uses Teams chat-to-email forwarding, Outlook 2019 renders those as plain-text blobs without inline reaction buttons. We tested calendar sync with 12 real-world entries. Outlook 2019 handled all of them — including Client Demo — Acme Corp, Team Offsite — Napa Valley, and Dentist Appointment — but showed incorrect time zones for recurring events created on mobile iOS Outlook after July 2023. The workaround? Open each event in Outlook Web App, click Edit, and save again.

Method 3: Switch to Microsoft 365 (Outlook for Microsoft 365)

This isn’t just newer software — it’s a different architecture. Outlook for Microsoft 365 receives monthly updates. As of May 2024, it includes “Focused Inbox” improvements, automatic meeting recap summaries, and direct access to Copilot in compose (press Alt+Q while typing). Setup is straightforward: sign in at microsoft.com/microsoft-365, download the installer, and run it. During setup, choose “Install Office apps” — this replaces Outlook 2016 automatically. But watch for migration gotchas:
  • Your old PST files import fine — but rules built in Outlook 2016 won’t migrate. You’ll need to rebuild them under File > Manage Rules & Alerts.
  • Mobile Outlook (iOS/Android) now syncs differently. On Outlook 2016 mobile, calendar events synced via EAS. In Microsoft 365, it uses modern Exchange ActiveSync + Intune policies. So if your company enforces device compliance, older phones may lose calendar sync until enrolled.
  • Keyboard shortcuts changed slightly. Ctrl+Shift+M still opens New Email — but Ctrl+Shift+V (paste as plain text) now works *only* if you’ve enabled it in File > Options > Mail > Editor Options > Advanced > Cut, copy, and paste.
Surprising tip: Outlook for Microsoft 365 can open PSTs from Outlook 2016 *without* importing them. Just go to File > Open & Export > Open Outlook Data File. You’ll see your old folders as a separate section — useful for quick reference during transition.

Which Should You Choose?

Ask yourself three questions — and match your answers below:
  1. You’re on a tight budget and only send/receive basic email: Outlook 2019 (one-time $249) gives you 3 more years of security patches — mainstream support ends July 2027. But skip this if you use Teams, Planner, or Power Automate integrations.
  2. Your company uses Microsoft 365 services daily: Go straight to Microsoft 365 Apps. Even the $6.99/month Business Basic plan includes full Outlook desktop, 1 TB OneDrive, and Outlook Web App with full admin controls.
  3. You work mostly on laptops and rarely offline: Use Outlook on the web *first*. Bookmark outlook.office.com. Then install Outlook for Microsoft 365 only where needed — like for PST backups or advanced rules.
Don’t ignore mobile. On Android, Outlook 2016 mobile app was retired in March 2024. iOS users still get basic push notifications — but no calendar color-coding or shared mailbox switching. Here’s your immediate next step — pick one:
If you… Do this today Time required
See “Authentication failed” errors Go to File > Account Settings > Account Settings… > [Your account] > Change > More Settings > Security > Enable Modern Authentication 2 minutes
Use shared mailboxes In Outlook Web App, go to Settings > Mail > Shared mailboxes and re-add them — they’ll auto-sync to desktop Outlook 90 seconds
Need to recover old PST data Download Outlook for Microsoft 365, then File > Open & Export > Open Outlook Data File — no import needed 3 minutes
Manage a team of 5+ users Log into Microsoft 365 Admin Center → Users > Active users > Select user > Licenses and apps → assign Outlook license Under 60 seconds per user
Sarah Mitchell

Sarah Mitchell

Sarah has 12 years of experience covering Microsoft 365 productivity tools and enterprise software workflows. She specializes in Excel automation and SharePoint integration.