There is a way to double check if there was a different "Reply-to" address after the mailing has been sent.
- Navigate to Campaigns dashboard
- Find your Sent campaign
- Click on the mailing ID #
- Click on the Source Tab
- Details will be found in the Header box:
- If there is no line titled "Reply-To", then the reply to address defaults to the "From" address
- Had the address been changed, it would look like this: