Emails erroring with "Invalid login: Username and Password not accepted"

This error usually means your Google app password was deleted after a Gmail password change, or the wrong password is stored on the sender.

Restore the existing sender with the Gmail steps in Reconnect your email sender. That guide covers creating a new app password, using Update Password, and verifying with Send test email.

If the message is a Microsoft 535 authentication error instead, the cause is usually disabled SMTP AUTH. See Why am I getting an 'Invalid login: 535' error with Microsoft 365?.

For first-time sender setup, use Connect Your Email to MCA Pilot.