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Better Late than Never for the Windows Desktop Client
The preview for External tagging for Exchange Online messages first appeared in March 2021 with general availability in October 2021. Microsoft 365 roadmap item 70595 covered OWA, Outlook Mobile, and Outlook for Mac. For no apparent reason, Outlook for Windows was conspicuously missing, perhaps because Microsoft anticipated faster progress with the Outlook Monarch client.
A year after the other clients received external tagging, builds of Outlook for Windows support the feature. I’ve been using it with beta channel releases (Version 2210, build 15726.20000 and later). External tagging works as expected with Outlook for Windows, but a potential reason for its delay is apparent at first sight.
Fitting External Tagging into Outlook for Windows
Compared to the other Outlook clients, Outlook for Windows is a antique beast of a program. Although Microsoft has tweaked Outlook’s design over the years, the same basic layout persists. Anyone who used Outlook 97 twenty-five years ago would recognize the latest click-to-run build. Sure, the menu is nicer, and Outlook boasts a reading pane to make it easier to triage a busy inbox, but the structure of mailbox resources, folders, and messages remains.
Preserving the essence of Outlook’s interface creates continuity for users. Change has happened over the years, but nothing to totally rebuild the interface in the same way that the Monarch project is progressing. The upshot is that Outlook’s interface is full of items and options, and the views used to display lists of messages are quite tight. The result is that the new external tag must fit into a confined space, and it looks like it (Figure 1).
I realize I am not a professional designer and that my reaction is very much that of an amateur, but the external tag adds more clutter to an already crowded Outlook screen. In any case, the UI is what it is.
As you’d expect, external tagging works exactly the same way as in other Outlook clients. Any email received from an external domain that isn’t marked for exclusion for tagging is tagged as external (see my previous article for details about how to exclude a domain). Most of the email I receive is from external domains, and even after excluding domains that I correspond with extensively, I see many tagged messages.
Raising User Awareness
To be fair, that’s the point. The idea of external tagging is to highlight these messages to users with the hope that people will pay extra attention to any links and other content. Organizations have used transport rules to stamp inbound email with similar labels for years and highlighting email does help. However, like any visual clue, user fatigue grows over time and the tags are probably less effective once they become part of the Outlook landscape.
External tagging also helps to avoid recipients falling into the trap of business email compromise (BEC). Many BEC attacks happen due to compromised accounts, but the removal of basic authentication from email connectivity protocols should reduce compromise through attacks like password sprays, meaning that attackers need to employ new tactics.
One is when email appears to come from an internal domain but really comes from a domain with a very similar name that’s set up by attackers with the aim of duping recipients. Humans might be fooled when an attacker swaps 1 for an l in a domain name, but a computer won’t be. Unfortunately, there’s no guarantee that people won’t ignore the external tag on an email that apparently comes from an internal sender.
External Tagging for Some, Not All
Adding external tagging to Outlook for Windows rounds out the Office 365 story. At least, if you use the click-to-run version. Perpetual versions like Outlook 2019 don’t include the necessary interface and Exchange Server doesn’t implement the feature for on-premises users. The classic approach of using transport rules to label external mail work in these scenarios. If you prefer to keep these methods, disable external tagging for Outlook by running the Set-ExternalInOutlook cmdlet:
Set-ExternalInOutlook -Enabled $False
Microsoft has probably done as good a job as possible to implement external tagging given the constraints of Outlook for Windows. External tagging works, it’s a valuable feature, and it will keep some out of trouble. That is, if you notice and respect the tags.
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