How can I send an email to all the customers?

Hi @monica4,

Welcome to the Community. I'd be glad to lend a hand with sending an email to all of your customers. 

To ensure that I'm on the same page, are you wishing to send a new email to all of your customers, such as advertising a promotion? If so, you can accomplish this with the following steps:

1. Click Sales on the left navigation panel.
2. Select Customers at the top.
3. Place a check-mark next to the customers that you need to email.
4. Click the Batch actions drop-down and choose Email.

I've included a brief video as an example:

In my experience, you will need to have Outlook installed and set as the default email service on your computer. 

Should you need to batch send sales transactions, please refer to the following link: How to Email or Print Multiple Invoices and Sales Forms at One Time.

I hope that this response finds you with a smile. Let me know if I can be of additional help. 
 

Good Evening, @Anonymous. 

Thanks for joining in on this thread. I hope your evening is going well. 

When emailing customers from your QuickBooks Online (QBO) account, there's no limit to how many clients you can send an email to. However, there's a chance that your network is getting caught up by the amount of information being sent out.

I recommend selecting as many customers as possible and then sending the email out again. This still allows you to send the email to your clients. You can use the instructions that my colleague provided above or this link about emailing and printing multiple invoices and sales forms. 

We're always working hard to improve this financial tool for you and other users. Should you need any further assistance, feel free to ask. The Community is here to have your back. Bye for now!