Sending through SMTP using gmail stops working every day

Sending through SMTP using gmail stops working every day

Hi. I use zoho for my custom domain email
I use the below settings for sending emails using gmail, but sending AS my zoho email

Every day, I get this error when sending an email

BUT when I re-enter the password in the gmail SMTP settings it works again for another day.

Any ideas how to fix this?


As an aside, I also get this message when forwarding emails to my gmail. It seems gmail doesn't like the spam emails that get through