Now in 2025 since September I've been having the same issue.

WE DONT USE GMAIL.

For my almost 300 invoice emails at the beginning of the month the system either sent one hundred, or just 3, or 11, and so on, sometimes not even 1.
Then just stops stating that it "lost connection to server and to check on my passwords, etc..".
Verified all with my Email provider, they say we are not blocked, that the emails that went, they followed and got to destination fine.
Something that took one click and automatically processed in about 1 hr, now takes all day and a lot of manual labor.
All tech personnel from Intuit, that have assisted in the last 3 months, asked for updates, and reconfigure the email service, for changing (editing, or deleting and re-creating the email).
All SMTP info we tried was certified by our email company, including various PORTS.
We tried using Intuit email service but our clients went "wild" because their SPAM services blocked, so we had to send 1 by one all again.
I see this problem is growing.
What can we do?
HELP !!!