Due to the architecture of an Exchange server, emails sent internally (within your organization) are not filtered for spam. And, if a message from an internal user ends up in the Junk folder of another internal user, there might be several reasons why it happened:

Emails were sent from outside of Intermedia

If you use SMTP devices or have a website that is configured to send out emails from an email address hosted with Intermedia to another users inside of your organization, emails sent from there will pass through mail filter checks because they are considered to be external by Exchange servers. As a result, they might be marked as Junk by mail filters.

One of the reasons why those emails may end up in Junk folder is failed SPF record validation. To prevent this from happening add device's IP address to an SPF record set up for your domain.

Another reason why they may end up in Junk is because they got a high spam score and were routed to Junk Folder as per Message Routing settings chosen for handling incoming Junk Mail on your account.

Local reasons: something is misconfigured in Outlook

If messages from internal senders end up in Junk, most often it is caused by one of the following local reasons:

  1. Outlook Junk Filtering
    Most Outlook clients have a built-in filtering mechanism that might mistakenly move legitimate messages to the Junk folder, this is why we recommend to have it off. To turn it off:
    Outlook 2010/2013/2016: Home > Junk > Junk E-mail Options > Options > set to No Automatic Filtering
    Junk Rule Win
    Outlook 2011 for Mac: Home > Junk > Junk Email Protection > Level > set to None.
    Junk Rule Mac
    Outlook 2016 for Mac: Outlook 2016 for Mac does not support client-side mail filtering so there is no way to disable it
  2. Outlook Plugin
    Note: applies to Outlook for Windows only.
    Check your active plugins in Outlook > File > Options > Add-ins > Go > uncheck any antivirus plugins you see there.
    Plugin
  3. Outlook Block List
     Check whether your company's domain/sender's email address is added to Blocked List:
    Outlook 2010/2013/2016: > Home > Junk > Junk E-mail Options > Blocked Senders
    Outlook Block Win
    Outlook 2011 for MacHome > Junk > Junk Email Protection > Blocked Senders (if you need to remove an entry from the list, make sure that Junk filtering is turned on)
    BlockMac
    Outlook 2016 for Mac: Home > Junk > Junk Email Preferences > Blocked Senders
    Outlook for Mac 2016 Blocked Senders

    OWA: Options > See All Options > Block or Allow
    BlockOWA
  4. Outlook Rules
     Check whether you have any Outlook rules that could move emails to Junk:
     Outlook 2010/2013/2016: > Home > Rules > Manage Rules and Alerts
    RulesWin
    Outlook 2011/2016 for Mac: Home > Rules > Edit Rules > Exchange
    Outlook for Mac Rules
    OWA: Click on the gear icon and go to Options > Organize email > Inbox Rules
    OWA rules