Stop Microsoft users sending 'reactions' to email by adding a postfix header

Original Article ↗ Hacker News Discussion ↗

How Outlook Email Reactions Work

  • Outlook/Exchange lets users “react” to emails; for other Outlook users, this shows as inline emoji on the original message.
  • For many non‑Outlook recipients, each reaction arrives as a separate “X reacted to your message” email, often with an image that may be blocked.
  • One commenter tested and found no simple distinguishing header; reaction emails look like normal mail plus the usual x-ms-* headers.
  • Gmail has added a similar emoji reaction feature, so this is no longer unique to Microsoft.

Postfix Header Opt‑Out and Technical Concerns

  • The blog’s approach is to add a custom header (e.g., X-MS-Exchange-Organization-DisableReaction: true) in outbound mail so Microsoft servers suppress reactions.
  • Some note this “fix” breaks DKIM because the MTA modifies headers after signing.
  • Alternatives discussed:
    • Rejecting such mails at SMTP time (sends a server‑generated bounce).
    • Blackholing them after acceptance (nicer for the recipient, confusing for the sender).
    • Simple content-based filtering on reaction subjects/text.
  • Several argue Microsoft should have shipped this as opt‑in based on known‑capable clients, not opt‑out via magic headers.

UX, Attention, and Email Culture

  • Many participants dislike reactions in email specifically:
    • Extra low‑value messages clutter inboxes and notifications.
    • Ambiguity: a thumbs‑up may mean “acknowledged,” “agree,” or just “saw this.”
    • Email is treated as “serious” async communication where explicit, textual replies are preferred.
  • Others like reactions as lightweight acknowledgments, especially inside a single Outlook/Exchange environment, reducing “OK/Thanks” reply‑all spam.
  • Some prefer read receipts; others find them invasive or misleading and routinely disable them.

Reactions in Chat, SMS, and Other Systems

  • Reactions are generally viewed as useful in Slack/Teams/IM: fast acks, less typing, reduced message noise if clients aggregate them.
  • Complaints arise when these systems leak into incompatible channels:
    • iMessage reactions forwarded as SMS text (“X liked ‘…’”) are widely seen as spammy.
    • RCS and Android/iOS now try to parse and collapse such texts, with mixed success.
  • Several stress that norms differ by medium: what’s fine in real‑time chat can be confusing or hostile in email.

Microsoft, Standards, and Historical Parallels

  • Many see this as another case of “extend” in “embrace‑extend‑extinguish”: leveraging a standard (email) while degrading interoperability.
  • Parallels drawn to:
    • Microsoft Comic Chat mangling IRC with extra metadata.
    • Exchange “recall” messages that only worked inside Exchange.
    • Wi‑Fi Sense password sharing and SSID _optout conventions.
  • There is mention of an existing RFC for email reactions, but uptake appears minimal; Outlook’s implementation is proprietary.