All the QuickBooks troubleshooting that the QB techs are posting are for people who don't know how to setup their email to work with QuickBooks, be either desktop, Pro, Pro Plus, etc. I spent over a month with many QB techs and non could fix the issue. After hours on the phone, they would come back and say it was a known issue. Well, it WAS a known issue and has been a problem since 2017 if you Google the errors you are getting and see what people are posting. We have QB Pro Plus on a subscription and it worked fine until a couple of months ago and then the error messages started coming up. We did notice that if you have a lot of invoices or estimates that are in the queue, but haven't been sent by email, you will get the Out of Memory error. However, sending emails plagued us and we too, had to work around.

As of Thursday, 03/16/2023, we had a very large Windows 10 update. Took 3 hours. Followed by a large QuickBooks update. We even had to uninstall and reinstall our HP software. When all these were completed, our QuickBooks is sending via email again. If you have not updated your Windows 10 and QuickBooks ( or just QuickBooks on Windows 11 ), then I suggest you try. It resolved our issue. You will not get a resolution through QuickBooks, level 1 techs.