What's Changing
Before your mailbox moves from HCL Notes to Exchange Online, there is one quick bit of housekeeping worth doing: finding and clearing out emails that carry very large attachments. Exchange Online has a maximum size of about 149 MB for a single email. Any message bigger than that can fail to transfer during the migration — and you don't want an important email left behind. A few minutes of cleanup now means a smoother move. The good news: this only affects a handful of emails. Almost everything in your mailbox is a few kilobytes and nowhere near the limit. You're only hunting for the rare giants.
Understanding Email Sizes
- 8K means 8 kilobytes — tiny, a normal email
- 26K or 43K — still small, no action needed
- 11.9M means 11.9 megabytes — a large email, but under the limit
- 40.7M means 40.7 megabytes — large, and worth a look
Watch for anything approaching or above 149M. If the biggest email in your mailbox is well under that, you're already done — no action needed.
Find Your Largest Emails in Notes
Step 1 — Turn off “Group by Date”
- Click the Show menu at the top right of your mail.
- Remove the check mark next to Group By Date.
Step 2 — Open “All Documents” and sort by size
- In the left sidebar, click All Documents — this shows every email in your mailbox, not just your inbox.
- Make sure the view is fully expanded so you can see the column headers.
- Find the Size column and click its header to sort by size.
Step 3 — Scroll to the biggest emails
- Click the Size column header again if needed so the largest emails are at the top.
- Scroll until you can see your biggest messages and their sizes.
What to Do With a Large Attachment
For any email at or above the 149 MB limit, you have two choices.
Want to keep it?
- Open the email and save the attachment to your network share or file storage.
- Once it's safely saved, delete the email or remove just the attachment.
Don't need it? Simply delete the email — that removes the attachment along with it.
Quick Reference
| Step | What you do |
|---|
| 1 | Turn off Group By Date in the Show menu |
| 2 | Open All Documents and click the Size column to sort |
| 3 | Sort largest first and look for emails near 149M |
| 4 | Keep it? Save to your file storage, then delete the email |
| 5 | Don't need it? Just delete the email |
What If I Miss One?
Don't worry about being perfect. If a large email can't be moved, it simply isn't migrated, and IT can help you recover or handle it afterward. Doing this cleanup ahead of time just makes the move cleaner.
Tips for Your Organization Staff
- When in doubt, save first, delete second.
- Not sure if a file is important? Ask your manager or the IT Service Desk before deleting.
- This is a one-time step before your mailbox migrates — you won't need to repeat it in Outlook.
Need Help?
- Check the Quick Start guide on this site
- Ask a colleague who has already been migrated
- Contact the Your Organization IT Service Desk
