Start/notes.ini Parameters/ICAL_SendAsMultipartRelated

ICAL_SendAsMultipartRelated

Parameter: ICAL_SendAsMultipartRelated
Short description: Controls the MIME format of outgoing iCalendar meeting invitations from the Domino router. With 0, Domino reverts to pre-12.0.1 behavior — standard workaround for O365/Outlook recipients.

Profile

Parameter
ICAL_SendAsMultipartRelated
Category
Mail / Router
Component
Server
Available since
12.0.1 (regression / workaround)
Supported versions
12.0, 14.0, 14.5, 14.5.1
GUI equivalent
notes.ini only (no GUI)
Possible values
0 = send without multipart/related (workaround) • 1 / not set = default since 12.0.1 (multipart/related bundling HTML+ICS)

Description

With Domino 12.0.1, the MIME format of outgoing meeting invitations was changed: ICS calendar data is since then sent together with the HTML body in a multipart/related envelope. While this form more closely matches the iCalendar/MIME recommendations, it does not interoperate reliably with Microsoft Exchange Online (O365) and Outlook on the Web — recipients there sometimes see the invitation as a plain-text mail or as a bare .ics attachment instead of as a processable calendar entry.
HCL documents the behavior and the recommended workaround in several knowledge base articles (KB0091299, KB0093004, KB0113204, KB0104418): with ICAL_SendAsMultipartRelated=0, the Domino router falls back to the earlier MIME layout, in which the ICS part and the HTML part are sent as separate top-level parts — the way Outlook and the O365 receiving chain reliably parse them.
The parameter takes effect for all outgoing meeting invitations the Domino router delivers externally via SMTP — regardless of whether they originate from the Notes client, HCL Verse, or iNotes/Notes for Web.

Example configuration

Set workaround in the server notes.ini:
ICAL_SendAsMultipartRelated=0
Activate without server restart via the console:
set config ICAL_SendAsMultipartRelated=0
Deactivate again (restore default 12.0.1+ behavior):
set config ICAL_SendAsMultipartRelated=1

Notes & pitfalls

  • Only affects the Domino router (SMTP send). Internal Notes-to-Notes delivery is unaffected.
  • Effective only after a reload of the routing configuration (tell router update config) or a server restart.
  • Only resets the MIME format; does not change the content of the ICS data itself.
  • Still documented as a workaround in 14.0/14.5/14.5.1 — when O365/Outlook is in the receiving chain, =0 is often the least painful solution.
  • Alternatively, the "Some invitees use other mail programs" toggle can be set in the Notes client when sending (see KB0093004) — but it works per invitation rather than server-wide.
  • Before activating in production, verify in a test profile that all relevant recipient mail systems (Notes, O365, Gmail, …) still process the invitation as a calendar entry.

Sources (HCL Product Documentation)