If you’d like to know if your email has been successfully received by the recipient, you can activate the return receipt option in your Outlook mailbox and Thunderbird email client. Read this article to find out how to enable this option.
When writing a message, click Options. In the Tracking group choose Request a Delivery Receipt. To ensure that your message has been read/opened by your recipient, check also Request a Read Receipt tab.
If you want to enable the Read Receipt for all of your emails, follow these steps.
1. Open the Outlook program/app and go to File > Options > Mail.
2. Under the Tracking section go to For all messages sent, request: tab and check the Delivery receipt confirming the message was delivered to the recipient's email server and, if you want to get a read receipt, check the Read receipt confirming the recipient viewed the message box.
3. Finally, click OK to save the changes.
1. Open Thunderbird and click on Tools. Go to Options > General tab.
2. Next to the Determine how Thunderbird handles return receipt, click on the Return Receipts button in the lower right.
3. Check the box next to When sending message, always request a return receipt.
You can consult this article to find out how to enable this option uniquely for specific email accounts.