We can verify the status of the email sent in QuickBooks Online (QBO), rccwes. I'm here to provide you with the details to check this.
Before we begin, could you please tell us which specific transaction you would like to check? Any additional information you provide would be appreciated and will help us offer you a more accurate solution to your concern.
If you're referring to sales transactions like invoices or estimates, you will see a Sent status indicating that these documents have already been sent to your receiver.

You can also check it in the Audit log; under the Event column, you will notice an Emailed status indicating that this transaction was successfully sent to your receiver.

For more information on emailing sales forms or reports in QuickBooks Online, please refer to this article: Email a sales form or report to multiple email addresses in QuickBooks Online.
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In QuickBooks Online, you have the option to either email or print sales forms after creating them. For more detailed information, please refer to this article: Email or Print Multiple Sales Forms in QuickBooks Online.
We're here to assist you in verifying the status of the transaction you've sent, rccwes. If you have any further questions or need additional assistance, please don't hesitate to leave us a comment. We will respond promptly.