New order notification is not sent to the admin

[bnymn]

When a customer places an order, (s)he receives an order confirmation email but admin does not receive any notification.

I have traced back the error to this file (vendor/magento/module-sales/Model/Order/Email/Sender.php:84)

It throws an exception with the following message "From Header set twice".

Preconditions

1. PHP 7.1.18
2. MySQL 5.7.22
3. Magento 2.2.4

Steps to reproduce

1. Login as admin.
2. Go to Stores -> Configuration -> Sales -> Sales Emails.
3. Go to Order section.
4. Make sure it is enabled.
5. Add your email into the field Send Order Email Copy To.
6. "Send Order Email Copy Method" to "Separate Email".
7. Go to your Magento store.
8. Login as a customer.
9. Make a new order.

Expected result

1. The customer should receive the order confirmation email.
2. The email address in the Magento admin which we have just added should also receive a copy.

Actual result

1. The customer receives order confirmatio email.
2. But admin is not notified, nor the copies are sent.

[bnymn]

I think the following issue is related with this one. #16165

[gwharton]

This is where the issue was first created. #11740

@bnymn, thank you for your report.
We've acknowledged the issue and added to our backlog.

[gwharton]

PR #16461 is awaiting review and will fix this issue.