Outlook Cached Mode Repeatedly Re-syncs Mailbox After Restart (Starts Again Around 3.99 GB)
Hi everyone, I’m experiencing a strange Outlook Cached Exchange Mode issue with a Microsoft 365 mailbox after a recent Windows rebuild and wanted to see if anyone has seen similar behavior. Environment: Microsoft 365 mailbox (Exchange Online) Outlook for Microsoft 365 Version 2605 Build 16.0.20026.20076 64-bit Windows 11 25H2 Fresh OS rebuild performed twice New Outlook profile created Office completely reinstalled OST recreated multiple times Issue: When Cached Exchange Mode is enabled, Outlook starts downloading/synchronizing mail normally, and the OST file continues to grow correctly. However, after every reboot or Outlook restart, Outlook again shows “Downloading…” starting from around 3.99 GB. Important observations: Online Mode works perfectly OUTLOOK.EXE closes properly after exit OST file is NOT deleted and continues growing Sync slider changes (1 month, 1 year, all mail) make no difference Disabling Outlook indexing did not help New Outlook profile did not help Reinstalling Office did not help Problem only started after OS rebuild Before rebuild, same mailbox worked normally in Cached Mode No pending office or windows update. It does not appear to actually re-download the mailbox from scratch because the OST size keeps increasing, but Outlook repeatedly processes/downloads from around the same 3.99 GB point after restart. Has anyone seen: Cached Mode replaying synchronization repeatedly after restart? Similar behavior on recent Current Channel builds? Security/EDR products interfering with OST synchronization state? Any known regressions with Outlook Version 2605 Build 16.0.20026.20076? Any suggestions or similar experiences would be appreciated.Sending a Welcome Message to New Employees Part 2
Recently, I wrote about how to use PowerShell to send a welcome email to new employees together with attached ICS files for corporate events. Although new employees can add the ICS files to their calendars (so the solution works), simply inviting employees to attend those events by updating the participant list with PowerShell is an easier and better approach. This article explains how to find calendar events, update participant lists, and update events with the Microsoft Graph PowerShell SDK. https://office365itpros.com/2026/05/27/new-employee-email2/
Sole Microsoft 365 Admin Locked Out After Phone Replacement / Lost MFA Device
I am the sole admin for a Microsoft 365 tenant and I am currently locked out after replacing my phone. The old phone was wiped before Microsoft Authenticator was fully re-registered on the new device. Authenticator was the only MFA method configured on the account. Current situation: password is known, Teams desktop sessions are still active, Authenticator cloud backup restored successfully, but all Microsoft security and admin pages still require approval from the old Authenticator registration. I cannot access Security Info, Entra Admin, or Microsoft 365 Admin Center because every path loops back to the dead MFA registration. I have already attempted Microsoft business support phone lines, Authenticator restore and recovery, and existing desktop sessions, but support queues are disconnecting and I cannot open business support tickets because the admin account itself is MFA locked. Tenant: lowepfg.onmicrosoft.com What is the fastest recovery or escalation path to force MFA reset or re-register Microsoft Authenticator for the tenant admin account?Prevent Microsoft 365 meeting invites from automatically appearing in users’ calendars
Hi All, We are trying to prevent Microsoft 365 meeting invites from automatically appearing in users’ calendars as Tentative until the user explicitly accepts the invite. Setting for Outlook Classic, New Outlook and Windows or Outlook Web. Need Microsoft recommendation on this one.Transfer MS Office 365 Business ownership from MSP to own MS Business account
Hello Everybody I need to transfer my clients MS Office 365 Business from current MSP to their own MS Business account. Current MSP very bad service. So, at the end they want to manage their Emails\Licenses on MS Admin Center. What are the steps on doing this?I built a free, open-source M365 security assessment tool - looking for feedback
I work as an IT consultant, and a good chunk of my time is spent assessing Microsoft 365 environments for small and mid-sized businesses. Every engagement started the same way: connect to five different PowerShell modules, run dozens of commands across Entra ID, Exchange Online, Defender, SharePoint, and Teams, manually compare each setting against CIS benchmarks, then spend hours assembling everything into a report the client could actually read. The tools that automate this either cost thousands per year, require standing up Azure infrastructure just to run, or only cover one service area. I wanted something simpler: one command that connects, assesses, and produces a client-ready deliverable. So I built it. What M365 Assess does https://github.com/Daren9m/M365-Assess is a PowerShell-based security assessment tool that runs against a Microsoft 365 tenant and produces a comprehensive set of reports. Here is what you get from a single run: 57 automated security checks aligned to the CIS Microsoft 365 Foundations Benchmark v6.0.1, covering Entra ID, Exchange Online, Defender for Office 365, SharePoint Online, and Teams 12 compliance frameworks mapped simultaneously -- every finding is cross-referenced against NIST 800-53, NIST CSF 2.0, ISO 27001:2022, SOC 2, HIPAA, PCI DSS v4.0.1, CMMC 2.0, CISA SCuBA, and DISA STIG (plus CIS profiles for E3 L1/L2 and E5 L1/L2) 20+ CSV exports covering users, mailboxes, MFA status, admin roles, conditional access policies, mail flow rules, device compliance, and more A self-contained HTML report with an executive summary, severity badges, sortable tables, and a compliance overview dashboard -- no external dependencies, fully base64-encoded, just open it in any browser or email it directly The entire assessment is read-only. It never modifies tenant settings. Only Get-* cmdlets are used. A few things I'm proud of Real-time progress in the console. As the assessment runs, you see each check complete with live status indicators and timing. No staring at a blank terminal wondering if it hung. The HTML report is a single file. Logos, backgrounds, fonts -- everything is embedded. You can email the report as an attachment and it renders perfectly. It supports dark mode (auto-detects system preference), and all tables are sortable by clicking column headers. Compliance framework mapping. This was the feature that took the most work. The compliance overview shows coverage percentages across all 12 frameworks, with drill-down to individual controls. Each finding links back to its CIS control ID and maps to every applicable framework control. Pass/Fail detail tables. Each security check shows the CIS control reference, what was checked, what the expected value is, what the actual value is, and a clear Pass/Fail/Warning status. Findings include remediation descriptions to help prioritize fixes. Quick start If you want to try it out, it takes about 5 minutes to get running: # Install prerequisites (if you don't have them already) Install-Module Microsoft.Graph, ExchangeOnlineManagement -Scope CurrentUser Clone and run git clone https://github.com/Daren9m/M365-Assess.git cd M365-Assess .\Invoke-M365Assessment.ps1 The interactive wizard walks you through selecting assessment sections, entering your tenant ID, and choosing an authentication method (interactive browser login, certificate-based, or pre-existing connections). Results land in a timestamped folder with all CSVs and the HTML report. Requires PowerShell 7.x and runs on Windows (macOS and Linux are experimental -- I would love help testing those platforms). Cloud support M365 Assess works with: Commercial (global) tenants GCC, GCC High, and DoD environments If you work in government cloud, the tool handles the different endpoint URIs automatically. What is next This is actively maintained and I have a roadmap of improvements: More automated checks -- 140 CIS v6.0.1 controls are tracked in the registry, with 57 automated today. Expanding coverage is the top priority. Remediation commands -- PowerShell snippets and portal steps for each finding, so you can fix issues directly from the report. XLSX compliance matrix -- A spreadsheet export for audit teams who need to work in Excel. Standalone report regeneration -- Re-run the report from existing CSV data without re-assessing the tenant. I would love your feedback I have been building this for my own consulting work, but I think it could be useful to the broader community. If you try it, I would genuinely appreciate hearing: What checks should I prioritize next? Which security controls matter most in your environment? What compliance frameworks are most requested by your clients or auditors? How does the report land with non-technical stakeholders? Is the executive summary useful, or does it need work? macOS/Linux users -- does it run? What breaks? I have tested it on macOS, but not extensively. Bug reports, feature requests, and contributions are all welcome on GitHub. Repository: https://github.com/Daren9m/M365-Assess License: MIT (free for commercial and personal use) Runtime: PowerShell 7.x Thanks for reading. Happy to answer any questions in the comments.
Latest MS Trend: abysmal AI phone support
Hello, I've just tried three times the MS 365 Support Phone Hotline. The AI Bot is designed to just hang up or provide an aka.ms/??? link which exactly leads to the problem that I am trying to contact support for. Thanks for nothing. Hope you fire also the people that worked on the Bot and not only your support hotline staff. It seems there are none left. I am going to recommend my company to move to a different product and drop ms ai slop. ByePrimer: How to Use RBAC for Applications to Control App Use of the Mail.Send Permission
The temptation to use the Mail.Send application permission in scripts can lead PowerShell developers into trouble because the permission allows access to all mailboxes, including sensitive executive and financial mailboxes. Fortunately, RBAC for Applications allows tenants to control the access that apps have to mailboxes and other Exchange content. All explained here with an example script to test RBAC of Applications. https://office365itpros.com/2026/02/17/mail-send-rbac-for-applications/
Cross tenant migration tools : New MS solution compared to Migration Wiz?
Hi, I'm looking for informations about advantages and limitations between new Microsoft Cross Tenant migration solution (Preview) and "Migration Wiz". Microsoft solution look more limited and doesn't seem to have Free/busy sync. What are the returns for those who did use MS cross tenant solution ? Thanks,Microsoft Unified Tenant Configuration Management
Unified Tenant Configuration Management (UTCM) is a new tenant configuration management solution that can monitor changes to over 300 resource types found within Microsoft 365 tenants. Currently accessible via Microsoft Graph beta APIs to all tenants, UTCM offers an alternative to Microsoft DSC and third-party configuration management products. No details are available yet about an admin UX, licensing, or availability. https://office365itpros.com/2026/02/03/utcm-beta/
