Outlook 2016’s New POP3 Bug Deletes Your Emails!

Yikes, looks like the new version of Outlook 20016 has broken the POP3 implementation. If you are currently using the “leave on server and  delete after x days” function, the you should check your account because it seems like that the new Outlook is actually deleting your emails almost immediately after retrieving them over POP3. You might also be seeing dupes.

TL;DR If you are using the Outlook 2016 to download from a POP3 server, you should disable automatic updates and/or downgrade to a previous version or else your emails are likely to be deleted almost immediately.

UPDATE 03/21/2016:
You can now just update to the latest version of Outlook to fix this problem. Inside Outlook, click on…

File->Office Account->Office Updates->Update Now

Note that if you turned off Office updates before, you should probably turn them back on now.


UPDATE 02/26/2016:
New and helpful Microsoft Knowledge Base Article here…

TL;DR: Disable automatic updates in File->Office Account->Update Options and then downgrade by entering this at a command prompt…

[code]"C:\Program Files\Common Files\Microsoft shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.6366.2068[/code]


About a week ago I started seeing dupes in my Outlook inbox. Later I noticed that other clients were not seeing new emails at all.

After hours and hours of painful research, I am almost certain that I’ve narrowed the problem down to a bug in the latest Outlook 2016 POP3 client UIDL database.

To prove it, you can do what I did….

  1. Download a fresh Windows virtual machine straight from Microsoft. While these VMs images are meant for testing browser compatibility, they are super handy for testing other things too since they are ready to run and super clean. I used VirtualBox to run the VM, but it doesn’t matter.
  2. Download and install a trial copy of Outlook 2016. Again, super fresh and super clean.
  3. Download and install hMailServer.  This is a clean and lightweight POP3 and SMTP server that you can install in about 2 minutes. Make sure you pick “use internal database”.
  4. From the hMailServer admin, add a domain “test.com” and then add a user “test@test.com” to the domain. You can safely leave everything at defaults.
  5. Launch Outlook without adding an account. We want to turn on logging before we do any POP3 so we capture everything.
  6. Enable logging under File->Options->Advanced->Enable Logging.
  7. Quit and Restart Outlook to actually enable logging.
  8. Now go into File-Add Account and manually add a POP3 account with the username “test@test.com” and POP3/SMTP servers “”. You can leave everything else at default since the default is to leave messages on server for 14 days.
  9. Do “send/receive” and you should see the Outlook test email.
  10. Use the “New Email” button to send a couple of test emails to “test@test.com”.
  11. Do “send/receive” a couple of times and you should see the new test emails. Then you should also eventually start seeing dupes. Bingo!

Now open up the file C:\Users\IEUser\AppData\Local\Temp\outlook logging\OPMLog.log.  Here are the lines that highlight the issue…


# List all messages on the server

2016.02.24 13:40:46 POP3 ( [tx] UIDL
2016.02.24 13:40:46 POP3 ( <rx> +OK 1 messages (1081 octets)
2016.02.24 13:40:46 POP3 ( <rx> 1 1
2016.02.24 13:40:46 POP3 ( <rx> .

# There is a new message #1, so retrieve it

2016.02.24 13:40:00 POP3 ( ==== Comparing server and local blobs ====
2016.02.24 13:40:00 POP3 ( 1 : new
2016.02.24 13:40:00 POP3 ( ==========================================
2016.02.24 13:40:00 POP3 ( Do deletions: LoS: yes, DA: 14, DoN: no
2016.02.24 13:40:00 POP3 ( ========= No blob changes =========
2016.02.24 13:40:00 POP3 ( ===================================
2016.02.24 13:40:00 POP3 ( [tx] RETR 1
2016.02.24 13:40:00 POP3 ( <rx> +OK 1081 octets
2016.02.24 13:40:00 POP3 ( done

# A little while later….
# List all messages on the server

2016.02.24 13:41:17 POP3 ( [tx] UIDL
2016.02.24 13:41:17 POP3 ( +OK 2 messages (3650 octets)
2016.02.24 13:41:17 POP3 ( 1 1
2016.02.24 13:41:17 POP3 ( 2 2
2016.02.24 13:41:17 POP3 ( .

# Now there are two messages, #1 (the one from a couple of minutes ago) and #2 (a new one)

2016.02.24 13:41:17 POP3 ( ==== Comparing server and local blobs ====
2016.02.24 13:41:17 POP3 ( 2 : new
2016.02.24 13:41:17 POP3 ( ==========================================

# Wait! What? Only one of those messages it new! Did you already forget about #1?

2016.02.24 13:41:17 POP3 ( Do deletions: LoS: yes, DA: 14, DoN: no
2016.02.24 13:41:17 POP3 ( [tx] DELE 1
2016.02.24 13:41:17 POP3 ( +OK msg deleted

# WTH are you DELETING my 1st email message!?! I told you to leave on server (Los) for 14 days (DA)!


The full log is available here showing the whole tragedy unfold.

After multiple calls with Microsoft, escalation is underway. I’ll update with details.

I do miss the old days when you could get straight to the application group with real problems, I think building walls around the engineers ends up hurting their situational awareness on stuff like this. All developers should be required to spend a certain amount of time every day fielding support calls. Makes for much better products.

UPDATE 3/1/2016:

If you are having problems downgrading…

  1. Try running the command as Administrator.

  2. If you are getting “Something went wrong” errors, try repairing your Office installation.


      • bigjosh2

        I really would love to get off Outlook and I *wish* I could use Thunderbird, but it does not even have some of the most basic features that use every day and it would take a huge amount of work to add them. It is surprising that after 20 years, Outlook is still the only full-featured email client. Maybe someone will make a good-enough web-based client someday…

  1. Steve

    I have exactly this issue ! Was set to leave on server for 30 days. Five email accounts all lost 30 days of email.

  2. Chris Hill

    This is escalating onto a BIG problem. How can you roll back the 2016 update?? And if you do how can you stop Microsoft updating again?

  3. Jeppe

    Thanks for posting this. I had just figured out that it was Outlook 2016 that was deleting my mails on the server. Good to know the issue has been reported to MS.

  4. Max

    I’m so irritated !! All my emails have been deleted from the server, with the config “remove from the server after 100 days”..
    Thank you MS
    And now I receive the same messages 3, 4, 5 times…
    crappy software

  5. Reiner

    Before I read your message and just before looking into the MS community, I thought somebody had hacked my mail account or I had indeed caught a virus…
    One can expect that such simple functions are tested BEFORE an update is made public available

  6. Angel

    Same issue with my emails on Outlook: Dups and inconsistent downloads to my mobile device. Lots of frustration. Let us know when Microsoft finds a fix. Using supplemental IMAP account in the meantime.

  7. David

    Same issue. Yes some of us do still use POP3 – try using IMAP on slow, intermittent rural mobile connections and you see why I went back to using POP. E-mails are downloaded to the local machines and can be read on or off-line and there’s a still copy for 100 days on the server that my phone can access using IMAP when I visit the big city – at least there was until this morning when Outlook cheerfully emptied 5 e-mail accounts with no warning or apology. Is Microsoft prepared to ask and pay for ISPs to reinstate millions of deleted e-mails from backups? I like Outlook, but the 2016 version has had a number of problems that really come down to inadequate testing. Have rolled back to previous version and turned off updates – doesn’t get my e-mails back though, so my phone is now devoid of all of the last 3 month’s messages.

    • Jeroen

      Use e.g. Mosh + SSH or have a server fetch your e-mail and then you copy it over from there. There is no reason to use POP3, just like there is no reason to use IMAP without TLS.

  8. Pingback: Importante bug en Outlook 2016 que provoca el borrado de correos | ULTREIA Comunicaciones | Soluciones TIC para su negocio
  9. Pingback: 1 – Outlook 2016’s New POP3 Bug Deletes Your Emails
  10. Pingback: Outlook 2016’s New POP3 Bug Deletes Your Emails | ..:: Frog in the box ::.. | ..:: Frog in the box ::..
  11. Pingback: Outlook 2016 Deletes POP Mail - Ryan's Tech Tidbits
  12. dog

    I don’t have a virtual box and I don’t have my own server. Does it work with just plain email from my ISP?

  13. Pingback: Anonymous
  14. johnfotiosblog

    Thank you Josh, I’ve had this issue for a week or so, no idea why. I disabled it “delete mail from server”, which let emails appear on my phone, but then saw lots of duplicates coming through on my outlook (as it would keep downloading from the server!)…

  15. Pingback: Outlook 2016’s New POP3 Bug Deletes Your Emails! • SafeNull
  16. bidthedog

    This has screwed me up too! Just noticed it – I’m going away next week, and I was hoping to have the last 90 days of my email available via my webmail, but noooo… this bug has to appear just at the wrong time!

    At least I’m not going crazy, and someone else is having the same problem :|

  17. Pingback: Macpro
  18. Pingback: Outlook 2016发现会删除邮件的bug - IT大道
  19. Pingback: Outlook 2016发现会删除邮件的bug - 来科技-来科技
  20. Pingback: Outlook 2016发现会删除邮件的bug | 陈丹的博客
  21. Pingback: Outlook 2016發現會刪除郵件的bug | Comeposts.com
  22. Pingback: Outlook 2016 clears POP mailbox on leap day | Shiftkey Software Blog
  23. Joseph Lee King, III MCP, SBSS

    The above scenario is true but the problem of the email getting deleted after being pulled to Outlook 2016 is also being caused by something else on our systems. As of Sunday 02-28-2016 at 7AM our online email box gets deleted every time we retrieve our mail. We have not applied the KB3145116 patch on our systems and I was originally using POP3 to pull the mail and changed to IMAP and it still deletes the mail after retrieving it which is supposed to never happen. I believe that a Exchange patch is at fault for this new condition that just showed up.

  24. Pingback: Outlook 2016 POP3 Bug Deletes And Duplicates Emails | Lifehacker Australia
  25. rammellel

    I tried a few different options but the only one that solved the problem consistently is to remove the latest Outlook 2016 update. I do not have my own server and just use a standard POP3 email account with my domain provider (running a small business). With the latest update removed, I can now download my email (to multiple devices as previously) and emails stay on the server until they are automatically deleted per my Outlook settings. Also, no duplicates downloaded as some are seeing. Per the recommendation from Microsoft, I have disabled Office 2016 updates until April 1.

  26. Aurora Partners Ltd

    Thanks for the detail. Had the same issue and applied method 2 from kb3145116. Seemed to work after reverting to previous version of Outlook. I then received BSOD System_Thread_Exception_Not_Handled error. Laptop reboots and displays message again in continual loop. Ended up having to use USB stick with Win 10. Tried alternate restore point which worked initially and then fault recurred. Had to reset Windows. Coincidence?
    Interesting that MS put a step in the workaround that says “Note Set a reminder on your Outlook calendar to enable updates on April 1, by clicking Enable Updates under Update Options.” ETA for a fix perhaps :-) and certainly not a good date as this is April Fools day in the UK.

  27. Ali

    I can’t thank you more! After spending a whole day with this issue, I have found this post and all Outlook clients now work as they should. Thank you so much again!

  28. Patrick

    I let my MSO2016 update to see if fixed, 16.0.6568.2034 is the newest branch, no change, still has that bug.

  29. Pingback: Outlook2016でメールがサーバから勝手に削除されるバグが発生しているようです。 | インターネットコンサルタントの元ネタ
    • Sammer

      Ya, ditto.
      Can you run your log again, and confirm office 365 version 16.0.6568.2036 is still deleting emails in POP3 and delete after X days checked?

  30. Jeff

    Microsoft posted a “resolution” at https://support.microsoft.com/en-us/kb/3145116, replacing their prior “workaround”. Updated to 16.0.6366.2068 and it now appears to be working fine (he said, crossing his fingers and knocking on wood). I didn’t even get any of the dreaded “Outlook may download all email one final time” duplicate messages. Ok, now I’m off to buy a lottery ticket. ;-)

    • Jeff

      Ok, a correction my my prior post. I updated to 16.0.6568.2036, not the incorrect version I incorrectly pasted in my prior incorrect post.

      OTOH, everything else is correct. No duplicates, no deleted messages (except the ones that were over my specified “delete after”). And that’s using the latest version available with the automatic updates: 16.0.6568.2036.

  31. niko

    Dude – thanks a lot for this … i am literally in hell for the last 3 weeks … and i just saw it … lol running 1 pop account with recent settings on google on 4 different machines…
    well maybe its my fault i didnt search for it earlier, but u are literally the only dude that has written about this recent problem …

  32. Roberto

    I am experiencing both problems, ie emails duplicated on one account (configured with Remove from server after days disabled) and emails deleted on another account (configured with Remove from server after days enabled). Every day I get new copies of all the emails, I reached 15 copies so far and I don’t have time to delete them.
    Thanks for posting.
    And thanks to Microsoft for this gift :-)

Leave a Reply to bidthedogCancel reply