By default, MHC sets the Google Calendar invitation option to "Only if the sender is known" with the goal of blocking spam but accepting invites from people you know. You can change this setting for your own calendar if desired.
Overview
As of December 1st, 2025, the default MHC Google calendar invitation setting is "Only if the sender is known". The goal of this is to balance blocking spam while also adding invites from people you know.
The key is what Google considers a "known sender":
- People in your contacts.
- People in your organization.
- People you've previously interacted with (e.g., sent emails to or from).
This setting automatically adds events to your calendar if the sender is known. For all other invitations (from unknown senders), it will send you an invitation email that you must explicitly respond to (yes/no/maybe) to add the event to your calendar.
You can change this setting yourself at any time if you are worried about missing calendar invitations from unknown senders. Keep in mind that if you change this setting you may get spam invites on your calendar. Some of these are from malicious senders experimenting with new phishing methods.
How the MHC default setting affects calendar invitations
| Sender Status |
What happens to the event |
Your action to Add to Calendar |
| Known (in contacts, organization, or prior interaction) |
Automatically added to your calendar |
No action needed. |
| Unknown (not in contacts, organization, or prior interaction) |
Not automatically added to your calendar |
You receive an invitation email and must select Yes to respond and add it to your calendar |
How to accept a calendar invite from an unknown sender
When you get a calendar invite from an unknown sender, the email with the invite information will include a prompt asking: "Do you want to automatically add this and future invitations from [this sender] to your calendar?"
You can select "Add to calendar" to say yes to that question.
Alternately, if you don't recognize the sender and believe the invite to be spam, you can select "Report spam"
If you only want to accept this particular invite and maintain the sender's "unknown" status going forward, you can just say "Yes" (or "Maybe") to the invite using the options in the email.
How to change your Google calendar invitation setting, if desired
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Open Google Calendar on your computer.
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In the top right, select the Settings gear icon, then choose Settings.
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On the left panel, under "General," choose Event settings.
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Find the section titled "Add invitations to my calendar."
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From the dropdown menu, select the option that makes the most sense for you:
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From Everyone: Will add Google calendar invites on you calendar regardless of who they're from, even if the initial email invite was filtered into spam.
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Only if the sender is known (MHC default): Will add Google calendar invites to your calendar if they're from an MHC email address, from someone in your Google contacts, or someone who you've accepted calendar invites from before.
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When I respond to the invitation in email: Will not add any invitations to your calendar until you accept them by interacting with the invitation email.