QB Desktop 2019 for Mac. Send 17 invoices by email. All 17 email message go through but the last 8 have no invoices. Resend those 8 and the last 3 had no invoices. Sent the last 3 and they all go through correctly. I suspect there is some interface problem between QB and Mac Mail, which is the only permitted setup. Really embarrassing when customers receive emails stating "here is your invoice" and it's not there - more than once. To say nothing of getting extra emails.