Delivery failures get the most troubleshooting attention, but a large share of daily Office 365 friction has nothing to do with mail not arriving at all — sync problems, mailbox permissions, and licensing confusion cause just as much lost time.
Outlook Desktop Not Syncing
When Outlook shows old mail or doesn't reflect changes made elsewhere (webmail, mobile), the cached Exchange mode local data file is often the culprit — it stores a local copy that can fall out of sync after a network interruption or an update. Toggling cached mode off and back on, or in more stubborn cases rebuilding the local OST file, resolves most sync issues that don't have a server-side cause.
Shared Mailbox Permission Confusion
A shared mailbox (info@, support@) that a staff member can see in the folder list but can't actually send from, or can send from but the reply shows their personal address instead of the shared one, is almost always a permissions or "Send As" configuration issue rather than a bug — the admin needs to grant explicit Send As (not just Full Access) permission for the shared mailbox to send correctly under its own name.
Mobile App Setup Confusion
The native Outlook mobile app and a phone's built-in mail app (configured via Exchange ActiveSync) behave differently — notifications, calendar sync, and shared mailbox access can work in one but not the other depending on which was set up. Standardizing on the official Outlook mobile app for company devices avoids a fair amount of this inconsistency compared to mixing native mail app configurations across different phone models.
Licensing Confusion
A user assigned the wrong Microsoft 365 license tier (one without Exchange Online mail, for instance) can appear to "not have email" when the actual issue is a licensing gap, not a technical fault. Checking the specific license assigned to an affected user in the admin center is a fast, frequently-skipped diagnostic step before assuming something is broken.
Calendar Sharing That "Doesn't Work"
A shared calendar visible to one person but not another usually traces to a specific sharing permission level (can view free/busy only, versus full details) set differently than the person requesting access assumed — reviewing the actual sharing permission on the calendar owner's end, rather than assuming a sync bug, resolves this in most cases.
The General Pattern
Most of these "Office 365 problems" aren't platform bugs — they're specific, checkable configuration states (a permission, a license tier, a cache) that look like mysterious glitches until you check the exact setting responsible. Working through the specific setting rather than restarting the app repeatedly resolves the underlying cause instead of masking it temporarily.
When to Escalate to Your IT Admin vs Microsoft Directly
Permission and license issues (shared mailbox access, license tier assignment) are almost always fixable by your own organization's Microsoft 365 admin without needing Microsoft support at all — these are configuration choices your organization controls. Genuine platform bugs or account-level anomalies Microsoft's own systems are causing are the cases that actually warrant a Microsoft support ticket; most day-to-day friction people attribute to "Office 365 being buggy" falls into the first, locally-fixable category.
