u/Actual-Thanks-634

Has anyone here dealt with orphaned OST files after Outlook crashes or account removal?

I recently had to recover an old Outlook mailbox and noticed the manual export methods don’t work if the OST file is disconnected. I tested a few solutions and found that tools with preview, date filters, and PST split options make the process much easier for large mailboxes. One thing I learned: always verify whether the software preserves folder hierarchy and attachments before conversion. Some tools skip metadata or corrupt formatting during export. I also found it helpful when the software supports exporting OST to PST, MBOX, EML, and direct migration to Office 365 or Gmail instead of only PST conversion. Has anyone here tried recovering very large OST files (50GB+) recently? Curious which methods worked best for you.

Technically, yes, but practically it's risky. Outlook's built-in import starts struggling above 4–5 GB. You'll see slow syncs, random hangs, and if Outlook crashes or your machine sleeps mid-import, you're starting over. For a file that size, skip the native import. A dedicated PST to O365 migration tool handles it much better, with no size limits, imports directly into Exchange Online, and runs in the background so users can be live on O365 straight away.

Using a reliable PST management or conversion solution helps reduce Outlook lag, maintain mailbox structure, and prevent data loss during migration.

Go to Options → Delay Delivery → "Do not deliver before". Saved me from sending emails too early multiple times. Hope this helps someone!

Had an OST file with 3 years of client work become a useless brick after my employer's Exchange account went down. Spent a day trying native fixes. None worked. OST files are tied to the Exchange account that created them — no account, no access. Eventually converted it to PST with a tool and recovered everything — emails, folders, attachments, all intact. The tool took maybe 10 minutes for what felt like an unsolvable problem. PSA: Export a PST backup before your last day at any Outlook job. In the future, you will be grateful.

Spent hours trying manual OLM migration methods before realizing Office 365 barely supports OLM files directly. Finally used a tool that imported everything without breaking folders or attachments. Has anyone else here dealt with old Outlook for Mac archives recently?

OST files are profile-specific and encrypted to their original profile. You can't open them directly in a new profile. You need to either reconnect to the original Exchange account or use an OST extraction tool to convert it to PST.

This happened to me too after a power cut. First, try this: go to your Thunderbird profile folder, make a copy of the MBOX file as backup, then delete the .msf index file next to it and restart Thunderbird. It rebuilds the index automatically and sometimes fixes minor corruption. If that doesn't work, you may need a third-party repair tool that supports MBOX format. Always keep regular backups of your profile folder going forward.

PST files grow silently, and most people never realize it until Outlook completely slows down. Converting older archives into PDF or MBOX and storing them externally is the fastest way to free up storage without losing a single email. You can also migrate PST data directly to cloud platforms like Gmail, Office 365, or Hotmail if you want to go fully cloud-based. Simple fix that most IT teams overlook. Let me know if anyone needs help figuring this out!

The simplest way is to use Outlook's built-in export option. Go to File → Open & Export → Import/Export, select Export to a File, choose Outlook Data File (.pst), pick your folder, check Include Subfolders, and hit Finish. This exports everything, including attachments, in one go. If you need a different format like EML, MSG, or PDF, a third-party tool works better since the built-in option only supports PST. Either way, always verify the exported file size afterward to confirm nothing got skipped.

I’m unable to send emails in Microsoft Outlook because they keep getting stuck in the Outbox and never get delivered.

Even after clicking “Send” multiple times, the messages remain unsent, causing delays in my communication.