Hi Karen Frost,
Welcome to Microsoft Q&A.
Unfortunately, you can’t set “No response requested” as a default for all meeting invites in Outlook on the web / Outlook.com. That option is only available per meeting (under Response options).
Workaround
Create an Inbox rule to automatically move or delete meeting responses (event replies), so your inbox doesn’t get flooded.
Path:
Settings > Mail > Rules > Add new rule
Then choose a condition like Type = Event response, and set the action to Move or Delete.
Please let me know if this proves useful to you, or if you would like further assistance.
I'm looking forward to your reply.
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