How to Disallow Outlook Reactions

How to Disallow Outlook Reactions

Disallow Outlook Reactions with Clients or Mail Flow Rules

Introduced in October 2022 as a method to allow people to respond to email with an emoji instead of a traditional reply message, I think it’s fair to say that customer opinion about Outlook reactions is divided. Some think that being able to send back a heart or thumbs-up is a fantastic and simple way to respond to email. Others dismiss the idea as a valueless frippery.

In a September 2023 blog post, Microsoft describes how organizations can control the sending of reactions and new client options to allow users block reactions for individual messages. The assertion that “millions of reactions are used every day” seems impressive but needs to be viewed in the context of 400 million Office 365 users and the 9.2 billion emails handled by Exchange Online daily (figure from MEC 2022 presentation). The blog says that Microsoft realizes that granular control over reactions, especially for email where it might not be appropriate to respond with an emoji, is important.

How the Disallow Reactions Option Works

All of which brings us to the functionality described in message center notification MC670444 (last updated 19 September, 2023) and Microsoft 365 roadmap item 117433. Essentially, the controls boil down to two technical changes.

First, the OWA and New Outlook (Monarch) clients have a new message option that senders can apply to disallow reactions for individual messages. Microsoft says that support for Outlook desktop and the Outlook mobile clients will “follow at a later date.” Figure 1 shows the option to disallow reactions in the OWA new message creation window.

How to Disallow Outlook Reactions
Figure 1: The disallow reactions option for an OWA message

When a client disallows reactions, it stamps the message with the x-ms-reactions header set to “disallow.” Clients that receive a message stamped with x-ms-reactions set to “disallow” remove the ability of the recipient to respond with an emoji. Figure 2 shows the presence of the x-ms-reactions header with disallow set. The existence of the header forces OWA to disable the option to reaction to the message.

Figure 2: The x-ms-reactions header controls if reactions are disallowed for a message

Second, the Exchange Online transport service implements a check for the x-ms-reactions message header as email flows through the transport pipeline. If a user responds to a message with an emoji using a client that doesn’t support disallowed reactions (like Outlook desktop), the transport service stops the response being updated for the original message. To implement organization-wide blocks, tenants can deploy mail flow rules to apply the header to specific messages.

Mail Flow Rules to Disable Reactions

The Exchange Online transport service applies mail flow rules to each message as it passes through the transport pipeline. One of the actions available for mail flow rules is to modify message properties by setting a message header. Figure 3 shows an example of a mail flow rule to set the x-ms-reactions header for all messages sent between people within the organization with the exception of messages with “Congratulations” or “Announcements” in the message body or subject.

Figure 3: A mail flow rule to disallow reactions

A variation on the rule is to disallow reactions for any messages sent by selected people. For instance, all email sent by senior executives, or everyone working in a country where emoji responses are deemed unacceptable by local custom.

The net effect of disallowing reactions through mail flow rules is that the only messages that people can respond to with emojis are those that match exceptions granted in the rules. Figure 4 shows a message that matches the exception included in the rule illustrated in Figure 3. You can see that OWA UI reveals the option to allow the recipient to respond with an emoji.

Figure 4: A message allowed by exception to use Outlook reactions

Administrative Controls Often Lag Behind New Features

Some will wonder why it took Microsoft a year to introduce controls for Outlook reactions. It’s always better when new features come along with administrative controls but it seems like the rush to introduce new functionality in cloud systems means that the surrounding administrative framework is lacking. That’s a pity, but at least the necessary controls are now available.


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