Outlook error when sending to Gmail

Anyone know why my Outlook 2017 suddenly stopped sending emails to Gmail addresses? It works fine from everywhere else, just not through Outlook. I keep getting this error:
'williamcruz19@gmail.com' on 5/31/2022 at 7:55 PM
550 recipient verification failed (williamcruz19@gmail.com) [95.178.172.174:56402:292443]
Is there any way to fix this? It was working perfectly fine before, then just quit on me :-(

What domain are you using for your email address? Is it just @gmail.com?

I'm betting you're actually running Outlook 2007 here, so if that's the case, the fix is almost certainly toggling on "Less secure apps" in your Gmail settings

I ran into the exact same headache yesterday with Microsoft Outlook 2010—ended up fixing it by following this guide:
https://www.slipstick.com/outlook/ou...-apps-setting/