Allowing .ICS calendar files to be sent to a group inbox via email

Contribute Feature

AI-generated summary

wesochuck reported an issue where .ICS calendar invites sent to a Discourse group’s incoming email address are not appearing as attachments in the group inbox, despite having the Allow ICS attachment extensions setting enabled. Moin initially clarified whether this pertained to chat or personal messages, leading wesochuck to confirm it involves a group with a custom incoming email address.

Moin suggested enabling the Allow all attachments for group messages site setting. wesochuck tested this but found no change; the .ICS files still failed to attach.

wesochuck provided a technical analysis, hypothesizing that Discourse does not recognize the text/calendar content type as an attachment, treating it instead as email body content. They suggested that the email/receiver.rb file would need modification to treat this MIME type as an attachment. tobiaseigen reclassified the discussion as a feature request. Finally, wesochuck noted existing work on calendar improvements in the Calendar and Events plugin and expressed hope that this functionality could be integrated.

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Sorry if I’m missing something obvious here. I’ve spent about 15–20 minutes searching and haven’t found anything that matches what I need.

I have a Discourse group with an associated incoming email address. My goal is for someone to be able to create a calendar event in Outlook, send the invite to that group email address, and have the resulting ICS invite appear as an attachment in the group DM thread.

I’ve already enabled the setting that allows ICS attachment extensions, but when an Outlook event email arrives in the group, no ICS attachment shows up on the post. In case it makes a difference, I’m running Discourse version 3.5.2.

Just to be clear: this isn’t about Discourse generating ICS files (e.g., via the #calendar-and-event feature). I’m only trying to get Outlook-sent invites to pass through as visible ICS attachments in the group thread.

Thanks for any insights!

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“DM” and “thread” are terms that are connected to chat in Discourse. Is this about chat or personal messages?

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Sorry for the confusion. This is a group with a custom incoming email address that we’re trying to get the .ics files to show up when that group email is sent a calendar invite email to the group address /messages/inbox for the group.

Group setup:

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Here is a sample, the info was sent, but .ICS attachment is missing. The group DOES get other email attachments.

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Have you tried enabling the Allow all attachments for group messages site setting?

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I had NOT turned that on… I was SO excited.

Sadly, when I turned it on, I didn’t see any difference, still no ICS:

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I’m 99% sure I haven’t vibe coded my way to a real solution, but I think could be narrowed down a bit.

  1. Incoming calendar invites are Content-Type: text/calendar;
  2. That is not one of the Content-Types that is recognized as an attachment by Discourse, it is just seen as part of the email body.

Several things would likely need to be changed:

  1. In discourse/lib/email/receiver.rb at a8cfcfb7ecb4f821391a16baedcc677f71b4db79 · discourse/discourse · GitHub it would need to recognize part.mime_type == “text/calendar” as an attachment type
  2. The system would need to basically create an .ics file attachment based on the data it finds afterContent-Type: text/calendar;

Not sure how likely any of this, but at least this is out there in case anyone else is searching around wondering why it isn’t working.

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I am shifting this over to Contribute > Feature because it seems to be a new feature request.

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I saw there were other calendar and event improvements being worked on over at: Current Projects - April 2026

So just giving this a bit of a bump in case someone already has the code opened up.

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