Email stopped working after update

[akurungadam]

Similar Issue, please if this helps.

Error Log - frappe.email.queue.flush

Regular email services like Gmail will restrict you to a limited number of emails per day. so thats what might be causing the error how many emails you are trying to send through your gmail? you should consider SMTP relay service like sendgrid or sparkpost https://erpnext.org/docs/user/manual/en/setting-up/email/email-account.html