Hi,
I hardly ever use this feature, but this was a good occasion to test is again.
I can confirm the error.
This is not a COPS or PHPMailer error but a (good) gmail feature.
Gmail blocks access from non-secure sources like PHPMailer used in COPS, probably because the used version or the implementation in COPS is outdated
.
To fix this you have to set gmail to accept less-secure access in the gmail settings. (log-in to your gmail account where you probably will find some warning e-mails from google. Then google how to fix it
).
I hope this helps you. I have it working again.
The question remains: "should you ignore google/gmail safety warnings?".
My answer:
A -
NOT if it is your main gmail account!
B - who cares if it's a dedicated COPS mailing account (and you clean it up regularly = delete sent an incoming mail so if your account is hacked no email addresses can be harvested.)