We have encountered a serious bug in Outlook 2013 which we believe could lead to lots of email being stored only locally, even though it appears to be stored on the server. This makes shared accounts impractical, and means that important emails are not backed up, even though they appear to be.
This bug is affecting accounts both on hermes and on our own imap archive server. Other people have reported issues with (for example) Gmail.
Unless and until this issue is resolved we recommend that anyone using Office 2013 either switch to using Thunderbird for their email, or downgrade to Office 2010 as Outlook 2010 is not affected by this problem.
Outlook normally makes a copy of email locally, and keeps this in sync with the email on the server. The issue is that sometimes it silently stops synchronising some email folders, and though they appear exactly like the other email folders they are only stored in the .ost file on the computer and are not saved on the email server. This seems to mostly happen when you create an email folder within Outlook 2013 and move some messages into it, or if you move a folder around within your account although we’re not sure exactly what triggers it to happen.
For most users there are no symptoms at all of the issue, and unless they are using a shared role account and notice that two users of the account are seeing different email folders, or they check on hermes webmail, it can go entirely undetected.
We have no idea how many people are currently affected but unaware of any problem, but have had repeated problems with two offices which are using shared accounts and there have been reported issues from at least three other people.
Temporarily fixing the problem within Outlook 2013
We’ve found the quickest way to get Outlook to show what is on the server, without losing any email which is stored locally, is:
- Use webmail to identify which folders are only stored locally and export them (and any calendars and contacts) into a .pst file.
- Make a back-up copy of this .pst file on the departmental file server.
- Close Outlook and delete the .ost file associated with the account which is having problems.
- Open Outlook and it generates a new .ost file for the account and you can transfer the missing email from the .pst file you created.
Unfortunately this does not stop the bug from happening again in future, and we have seen it recur immediately when we attempt to upload the missing email folders back to the server.
We note that .ost files are only readable by Outlook 2013 and by the account they were originally associated with, which is why we export to a .pst file rather than just making a copy of the original .ost file.
Migrating to Thunderbird
Thunderbird cannot read .pst or .ost files directly but can import email and other items such as contacts from Outlook. It is sometimes easier to import the missing email into Thunderbird before attempting to upload it back to the server.
Downgrading to Outlook 2010
When downgrading to Outlook 2010 any calendars, contacts and unsynchronised email will need to be exported to a .pst first and then imported back into Outlook. Make a note of your account settings before the downgrade as accounts are not migrated automatically.
Other bug reports
In September 2014 the University Information Service (formerly the Computing Service) mentioned a bug with Outlook 2013 which causes it constantly upload duplicate messages to the server, and we have seen a couple of cases of this within the Engineering Department too.