No invoices sent this month have reached customers

Hi Dee Noyes Thanks for reaching out to us here on the Community. We haven't had any reports of similar instances to what you're experiencing and we're not aware of any updates that may have caused the issue. Were the invoices that were sent to your customers recurring transactions or were they created/sent individually?

Hi @Dee Noyes 

The fact that the cc'd emails have reached your inbox shows that the QB/Intuit servers have done their bit - the emails have been sent out.  The problem lies in the workings (or not) of email.

QB/Intuit's servers probably send out millions of emails a day.  Every now & again, some of their addresses get blacklisted by other email servers (either intermediate or end user) - essentially marked as senders of spam.  When that happens, most end-users will find the QBO emails in their spam/junk folders.  However, many corporate systems will either quarantine the emails or delete them without further checks.

QB/Intuit can/should be constantly monitoring the published blacklists & getting their servers removed.  How efficient they are at doing that is a question you can probably answer yourself.

If customers cannot check their spam/junk folders your only viable workaround is download & send the invoices from your own email account (or cc/fwd as you have done).  That will be much more reliable as your customer's email system will probably recognise your address as a contact & be more likely to allow emails through.

Hope this helps (or at least, explains).