Change your Salesforce 'Reply To' email address - User Email Settings
Salesforce Classic
1. Click your username
2. Click My Settings.
3. In the Quick Find box, enter My Email Settings. Click on My Email Settings
4. Update the "What email address would you like to use as your return address?" field to the desired "Reply To" Email Address.
5. You can change how you would like your Name to appear by changing the Email Name.
6. Click Save.
Lightning Experience
1. Click on your avatar.
2. Click Settings.
3. In the Quick Find box, enter My Email Settings.
4. Update the "What email address would you like to use as your return address?" field to the desired "Reply To" Email Address.
5. You can change how you would like your Name to appear by changing the Email Name.
6. Click Save.