Prevent Exchange Online from moving Mails to Spam folder


Exchange admin center -> protection -> spam filter


We don't want mails to be sorted away in Spam folder. We want to keep Spam in inbox. For all users. So I changed the spam settings from 'move to Spam folder' to 'prepend subject line with text'. Text is 'MS_DETECTED_SPAM' (see attached image). Ex On puts the text in front of the original subject line but still moves the mail (with the altered subject line) to user's Spam folder.  How can I prevent this? The internal compliance rules require this.

11 Replies

Hi Robert,


That email's happens within OWA or Outlook ?


The best way to view the problem is only use Webmail without Outlook client, because the Outlook client can also put the mail on Spam folder.

This happens in both OWA and Outlook Client. If I try to kill the Outlook client, I won't survive this. ;)

Hi Robert,


You need to test use only OWA (Outlook Closed in any device) to see if the issue that you are experience is from Office 365 services or Outlook client.


And please see this article

Apart form being marked as Spam, messages can end up in the folder if they are marked as Phishing (read for example this recent blog post: or if the Outlook junk filter acted on them. Looking at the message headers should give you an idea what happened, and you can also run a message trace in the EAC/SCC to get additional information.

You can create a rule to set all your messages SCL to -1 to prevent it going to junk.
Setup a rule to do the following. I do this since all my spam goes through another external spam scan solution first.
Set the spam confidence level (SCL) to '-1'

In both worlds. We have users who never use the Outlook Client. And we have other user who never use OWA. Both types of users are affected.

We tested this. The Outlook Client (for Windows or Mac) is NOT the source of the problem.

This is not what we need. The mails should be flagged as Junk. But they should not be moved to the Spam folder.

They still get flagged as Junk by your E-mail gateway, all that flag does is prevent Exchange server from moving to Junk. I don't know how your mail flow happens, but Mine goes through spam filtering first, gets tagged, etc. Then into Exchange which that flag will prevent from moving into the folder.

Hi Robert,


In that case is you continue to have issues with those tests and the configurations are ok, I sugests to open a Support Ticket on Office 365 portal. 

I've had the same idea. Unfortunately, I haven't had any good experiences with 1st-level support in the past. Usually they don't understand me and the whole thing ends up as a waste of time. This was completely different one to two years ago. But maybe I really don't have another option.