How to Change Email Logo in Magento 2
Step 1. Admin panel > Content > Configuration (under Design)
Step 2. In the Configuration page, you will see a list of default website, then click on Edit under Action column.
When the page is opened, scroll down to Transaction Emails section and click on it.
Step 3. In Transactional Emails, you will see a list of logo settings for your own email including:
Logo Image: different types of file are allowed (jpg, jpeg, png). Here you can upload your desired email logo with a high-resolution display.