I just got my wife a new PC. No complaints otherwise, but I installed a new version of Office, including Outlook (Microsoft Office Professional Plus 2016/Outlook 2016 MSO 64-bit). It is running Windows 10.

She works quite a bit from home and uses Outlook for her work mail. I copied all the email settings from her old Outlook to this new version. She called her work's ISP and they got her all of her old messages and had her set up an .ost file. I've used .pst files before, but never ost (she had a .pst on her old PC). Outlook worked fine on her old PC with an older version of Outlook, but it is incredibly slow with this new version.

I'm a software engineer, so I can usually fix these issues pretty quickly, but this one has me beat. Symptoms:

  • Sending a message takes a minute or more
  • An item sent can take 15 minutes or more for her to receive
  • At the bottom of the Outlook window, a "working" bar appears saying "Synchronizing 'Inbox'" (other folders appear sometimes, like 'Sent items'). It never goes away.
  • A Send/Receive bar at the bottom (next to "working" bar) goes about halfway, and never completes.

I tested the email account settings when setting it up, and they completed fine, but it still took 10 minutes or so to receive the test email.

I know problems like this are hard to diagnose and fix, but I'd appreciate it if someone could at least give me some things to try. To answer the obvious, yes, I did shutdown and reboot (several times).

  • I suppose you've tried sending with your Anti-virus disabled? Maybe the AV is scanning the transmission?
    – bgmCoder
    Commented Mar 13, 2016 at 22:34
  • Well, it's just using Windows Defender and the email is just plain text, so I would assume there is nothing much for AD to scan, even if it is trying to scan the emails. Commented Mar 14, 2016 at 0:17
  • Is the account set up as IMAP or POP?
    – bgmCoder
    Commented Mar 14, 2016 at 1:43
  • It is IMAP/SMTP. Commented Mar 15, 2016 at 1:08

4 Answers 4


Outlook is full of settings that are difficult and non-intuitive to locate.

One thing that could cause a message to take longer to send (that is, to leave Outlook) is whether it is already synchronized with the server or no.

Check this setting:

File > Info > Account Settings (button) > Account Settings (menu item)

And find your mail account in the E-mail tab and choose Change (should take you into the Account Settings panel)

Check that Mail to keep offline is set to All:

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Another thing to try is, in the same Account Settings panel, click on More Settings then go to the Advanced and make sure the Purge items when switching folders while online is checked. The reason I suggest this is that (unless I'm wrong) it may perform some cleanup on the local db.

Also, in that same Advanced panel, I have for Server Timeouts set to 1 minute. Maybe that could help?

Here is something I found which has a few more ideas (Bear in mind I have not tried any of these things):

Make sure Outlook is closed. Then locate and run scanpst.exe with your *.pst outlook data file as the parameter. (This is the Inbox Repair Tool)

If that doesn't work, use your Office CD to run a repair.

Finally, try opening Outlook in safe mode by typing this in the RUN box:

Outlook.exe /safe
  • Thanks for the suggestions, but I already had all those settings selected. Meanwhile, Outlook endlessly synchronizing and Sending/Receiving... Commented Mar 15, 2016 at 1:10
  • I updated my answer with some more ideas for you.
    – bgmCoder
    Commented Mar 15, 2016 at 3:39
  • Okay, thank you. I will try them tonight. Have the head off to work now! Commented Mar 15, 2016 at 11:51
  • I ran the repair tool and it found errors. It said it repaired them, but it still gives us the endless "synchronizing" message at the bottom. But now it sends and receives immediately, so I'll call this a fix. Thanks for the help! Commented Mar 17, 2016 at 1:08

I am having a similar problem-outlook 2016 opens and doesn't receive email for over 10 minutes. When I click on "send/receive", nothing. However, there is another option/icon on the toolbar, "update folder", and when I click on it, I receive all my current email. It has a folder icon and arrows on top and bottom of folder.


Most likely the issue is with the OST file. All versions of Outlook create an OST file. On some systems it is the only database with your email (when email is downloaded and removed from the server) on others, it's just a copy. Outlook will recreate the OST if it's ever removed but it can only download the emails the server has. That being said I would try this: Have your wife go through her emails and move any messages she wants to keep into a PST file. Please remember to do all folder, sent, subfolder, etc.. Once that is done, close Outlook and backup the OST and PST to a different device (memory stick, external HD, Google Drive, MS Cloud...). Rename the OST file by changing the extension to BAK (I use this because it's easy to find and remember). Reopen Outlook and allow it to recreate the OST and download all current items. Try working with Outlook once it's finished and see if it isn't working better.


One thing that seems to work sometimes is clicking on the send/receive buttons, then restarting Outlook. This is not a solution, but may be a clue.

  • Thanks. This was solved a while ago, but it required some back and forth with the ISP. Thanks! Commented Jun 20, 2018 at 14:26

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