Some not all of my clients invoices are going into their spam files, how can this be stopped?

It's good to see you here in the Community, @bryan-ecleisurec.

I'll share some information on why sent invoices go to spam folders.

Many email programs use various blocking mechanisms on their mail servers, thus causing QuickBooks emails to go to spam folders. Also, there are email servers that don't accept mail from server IP addresses without reverse DNS entries that match the domain name that the server alleges to be representing. This is an anti-spam measure to prevent spammers from pretending to deliver mail from well-known domains.

In this case, you'll need to configure your server to allow mail to pass through your mail servers and accept QuickBooks Online mail server hostnames and IP addresses. To do so, you can follow the steps in this article to add the host names and IP addresses depending on your email setup: Configure server to accept QuickBooks Online mail server hostnames and IP addresses.

Most importantly, I suggest seeking help from an IT expert on configuring servers to ensure it is set up correctly.

Come back to this post and let me know how it goes, @bryan-ecleisurec. I want to make sure you're taken care of.

You may also want to view the status of your sales transactions in QuickBooks. You can go to the Sales menu and select All Sales.

Wishing you all the best!