Netgear R7000 Readyshare Vault -- email notification error from Gmail.

I have been using R7000 backup to vault for over a year and have never been able to get verifications of backups through Gmail. I tested "test email notification"

First message:
"Failed to send email notification.
Details:
Unexpected MAIL FROM response, last Response; 530 5.7.0 Must issue a STRTTLS command first. b188sm10074itc9 - gsmtp"

I fixed that by checking "[]Use SSL", but email notification still isn't working.

Second (current) Message:
"Failed to send email notification.
Details:
A graceful disconnect had occurred, Last Response:"

What could be my problem?

Does that mean that email verification doesn't work for the R7000 and nobody has been able to fix it?

Here is what I tried:
SMTP address = aspmx.l.google.com
port = 25
[ ] require authentication = Not checked
email = stanhilliard1936@gmail.com

Here is the error:
A connection attempt failed because the connected party did not properly respond after a period of time., or established connection failed because host has failed to respond.

The backups are going to a SSD drive connected to the router by USB.

I don't think 2FA at Gmail's smtp is the solution because I just tried using the smtp at my Comcast account and that fails too:

Here are my settings for using Comcast:
smtp server - smtp.comcast.net
[X]use SSL, Port = 465, or [ ]use SSL, Port = 25
Email - stanhilliard@comcast.net
Checked [X] require authentication
shilliard@samplingplans.com
mypassword

Failed to send email notification.
Details:
"Unexpected SMTP Login response, Last response:"

Since authentication has failed with three smtp servers, I think the problem is in the way the R7000 handles the authentication.

Experimenting further, I used port = 587 [X] SSL as per ANSWERED: Having trouble connecting your xfinity.net email to an email client?

Result:
Failed to send email notification.
Details:
Unexpected AUTH LOGIN password response, last response: 535 5.7.0 ...authentication rejected (1)

EDIT: I tested the sign-in at Comcast again and the password works when entered manually.