To hide ads that can't be blocked from downloading entirely, AdBlock inserts a large stylesheet into every web page you visit. Normally this works just fine―unless you are a Safari or Microsoft Edge user who sends email from Outlook Web Access (OWA; also known as Microsoft Office 365, Office365.com, or an Exchange Server account). Because of the way the OWA website is written and how Safari and Edge work, that large stylesheet from AdBlock is also inserted into every email sent from OWA. This makes mail servers and your recipients' mail clients think your emails are spam! Again, this issue occurs only in Safari and Edge and only when sending email from OWA (Office365.com).


You'll find that email sent from OWA after pausing or uninstalling AdBlock are not considered spam. That's because AdBlock is no longer inserting that large ad-hiding stylesheet into the messages.


Therefore, the workaround is to whitelist the OWA website so that AdBlock won't run on it. You may see some ads along with your mail, but at least the email you send will get through!


Whitelist the Office365.com domain

We whitelist outlook.office365.com with the following filter, which is part of the AdBlock Custom filter list:


@@||outlook.office365.com/$document


AdBlock Custom is enabled by default when you install AdBlock.


Whitelist a custom domain

If you use a custom domain for your Office365 email, you'll need to whitelist that domain yourself.

  1. Log in to your Outlook Web Access account on your custom domain.
  2. Click the AdBlock button and select Don't run on pages on this domain.
  3. Click Exclude.

The page will refresh and further emails should not be considered spam.


I'm not using Safari or Edge and I would like to disable that filter

If you use Outlook Web Access with Chrome, which isn't affected by this issue, you may prefer to disable the whitelist so that you don't see ads in your OWA mailbox. Here's how:

  1. Click the AdBlock button and select Options.
  2. On the GENERAL tab, make sure I'm an advanced user, show me advanced options is enabled.
  3. On the CUSTOMIZE tab, click Edit next to Edit disabled filters and type or paste the following filter rule on a new line inside the large text box:
    @@||outlook.office365.com/$document
  4. Click Save.
  5. Refresh the OWA tab.