New Acumatica system email accounts return "username or password not accepted" error

Question

I have a single system email account (a Google G Suite address at [email protected]) set up in Acumatica that has worked for years, and continues to work. However, upon adding other G Suite addresses so our sales team can use their own addresses in Acumatica, even with identical server settings, they always return the following error:

The mail send has failed. 535-5.7.8 Username and Password not accepted. Learn more at

I've tried it with existing accounts and creating brand new accounts. I know the credentials are correct; I've turned on the "Less secure app access" setting in G Suite that solved similar problems to this in the past. Nothing seems to work, and the stack trace points to parts of the business logic that are - as far as I can tell - proprietary, so we can't really dig into it any further.

Here's the whole trace:

4/3/2019 10:26:10 AM Error:
The mail send has failed.
535-5.7.8 Username and Password not accepted. Learn more at

at PX.SM.EMailAccountMaint.a(Action A_0, String A_1)
at PX.SM.EMailAccountMaint.b(IEnumerable`1 A_0)
at PX.Data.PXLongOperation.<>c__DisplayClass17_0.b__0()

Answer 1

Well, this is barely an answer, but it turns out that having your login information - even if it is correct - in the System Email Accounts -> Advanced Settings -> Security section of Acumatica breaks everything. I don't know if this is even a reproducible bug - I found it by trying to test the same thing in our dev environment, which is an exact copy of our live environment, and saw that, for some reason, the [email protected] address that has always worked had different settings there. I changed the new account in the live environment to match those settings, and it started working. Computers are stupid.