Planner - Plan 1 - Welcome message

Hi, unfortunately you are not overlooking a setting. Microsoft’s current Planner notification documentation states that the welcome email sent to plan members cannot be turned off. The most practical workaround is to create and configure the plan before adding all members, then add them only when the plan is ready and let them know that an automated welcome message will arrive. Reusing an existing Microsoft 365 group may help with membership management when that matches your governance model, but I would test it with a small group first because membership-related notifications can still occur. I would be cautious about suppressing the email with a tenant-wide Exchange mail-flow rule, since that could accidentally hide legitimate Planner onboarding messages for other teams