Problem using Beckhoff PLC to send email via gmail

I am trying to use my Beckhoff PLC to send emails. I am using a Gmail account that I just created. Apparently Google has removed “Less Secured Apps” in the mail app which allowed to me to use PLCs to send email in the past using a gmail account.

My PLC gives an error for Wrong username or password even though they are both definitely correct.

How else can I do this?

I want to test this in-house before I install it a customer at which point I can use their email hopefully without problems.

I have no experience with Beckhoff, but widely use Gmail on other platforms. Since the removal of 'Less Secured Apps' option, you now need to set up 2-Factor security on the account.
After this is setup you can create an 'app password' specific to your device. I've found this option to be much more reliable that the old 'Less Secure Apps' option.

At this point your customer's SMTP server is probably your best bet, unless you can setup something yourself that's internet facing.