Office 365 and Junk E-Mail

  1. Incoming Mail Detection
  2. SPAM in the Inbox
  3. Mislabeled SPAM
  4. Emails and SPAM Redirection/Forwarding
  5. Checking Outgoing Mail for SPAM

1. Incoming Mail Detection [menu]

There are two places to analyze emails and marked as spam:

  • on the central mail server. ***** SPAM! ***** is added to the subject of spam messages, and the header “X-Spam-Flag: YES”  is added to the message. In Office 365, these emails are automatically included in the Junk E-mail folder.
  • On Microsoft servers: Identified spam is included in the Junk E-mail folder, there is no ***** SPAM! ***** string in the subject line.

The user can influence the classification as spam using safe and blocked senders lists. Advanced users can create rules to filter incoming mail.

The test for infected attachments is also performed at both the central mail server and Office 365. The recipient will not receive an email with a virus in the attachment.

2. SPAM in the Inbox [menu]

If the message is not marked as spam, you have three remedies that can be combined:

  • You can report the Czech spam to the Office for Personal Data Protection.
  • You can add the sender to the blocked sender list.
  • You can report spam to Microsoft to help improve their antispam solution.
Please report/mark only spam. No conference invitations, social news, or business communications with functioning possibility to unsubscribe.

Unsubscribing is supported in both Outlook for Windows and the web interface. For an email, the unsubscribe option is offered if it contains a List-Unsubscribe header.

3.Mislabeled SPAM [menu]

It is advisable to check the Junk E-mail folder from time to time. If you find a regular email in spam, you can:

  • Add the sender to the Safe Senders List.
  • Move the messages to the Inbox. After moving, you can view it with pictures.
  • In the web interface, there is a menu option Not Junk – when you use it, the email moves into the Inbox, the sender is classified as safe, and it offers the possibility to report incorrect classification to Microsoft.

Email messages in the Junk E-mail folder are automatically deleted after 30 days of delivery.

4. Email and SPAM Redirection/Forwarding [menu]

When redirecting messages using a simple option, all emails, including spam, are redirected.

Instead, if you create an inbox rule, the spam will not be redirected.

5. Checking Outgoing Mail for SPAM [menu]

Microsoft also checks outgoing mail for SPAM. If a user marks more than 100 outgoing emails (only recipients are considered) as SPAM within 24 hours, it will block the user from sending mail outside VŠE. In this case, send a renewal request to

Blocking of mail sending occurs in the following situations:

  • The user is a phishing victim and the attacker has misused SPAM access credentials.
  • The user has sent an email to hundreds of recipients, and over a hundred addresses were invalid (rejected on target servers).
  • The user sent an email to hundreds of recipients, and an older email with strange formatting was included.

Unblocking a specific account is limited to several attempts (we have not been able to come to the exact number).