Has anyone received the error message, "Unable to send email, delivery server down?"

Let's get rid of this error so you can get back to working order, @byrdsnestheating.

The error you've received may cause by your browser's data. To get this fixed, let's try accessing your QuickBooks Online (QBO) account via a private browser. This way, we can check if it's a browser data issue.

Press this shortcut key on your keyboard to open a private browser:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Safari: Command + Option + P

Once logged in, go back and try to send an email again to double-check. If this works, it means that you need to clear the browser's cache so the system can start fresh. If you get the same result while using a private browser, I recommend switching to a different one.

You might also want to take a look at your sales transactions in QBO. Here's an article you can read: View sales transactions.

Keep in touch if you need any more assistance sending emails in QuickBooks Online. I've got your back. 

Receiving notice that delivery server dowm

Yes, been having the "Delivery Server Down" error all morning. It's being reported by numerous other users too. Standard QB instructions guide for fixing issue isn't working. Issue is occurring with customer I've been invoicing the exact same way for 2 years.

Thanks for joining the thread, @ILCD.

Upon checking, I've found out that there's an ongoing investigation related to the Delivery Server Down error message. 

Currently, our engineering team is already working on fixing this issue. Have you been added to the notification list for this investigation number? If not, I'd suggest contacting our QuickBooks Support Team to add you to the list of affected users. I'll show you how.

1. Click the (?) Help icon in the upper right-hand corner of the Dashboard.
2. Select Talk to a Human.
3. Enter a short description of your concern and press Enter.
4. Click I still need a human.
5. Select Contact Us to connect with our live support.
6. Choose Get a callback.

For more details about our support availability, refer to this article: Contact Support. 

In the meantime, I'd suggest visiting our Community Help website. This website shares helpful articles to read on different topics about QuickBooks. Just select a subject from the Topics drop-down menu.

Thanks for coming to the Community. I look forward to hearing from you again.

You’re a clown @Mark_R 

Site wide issue and you’re telling her to go to a private browser? Get a clue. I hope you don’t get paid for this.