A ‘from address’ is the email address your contacts see in the From field when they receive an email from you.
Choosing an effective ‘from address’ that’s consistent with your brand can help build subscriber trust, improve open rates and your campaign’s deliverability.
It’s best practice to choose a ‘from name' that closely matches your ‘from address’ - e.g., if your brand name is SAMPLE MARKETING, subscribers will expect a similar email address, such as ‘email@example.com’
You can set your default ‘from’ name and address in Email settings.
Changing the ‘From address’ and ‘From name’ won’t have a negative effect on your deliverability as long as they are consistent with your brand.
Reply to address
When a subscriber clicks Reply to an email you’ve sent them, the reply message is sent to the email address listed in the From: header, unless you have set a default ‘reply to address’ in Email settings.
Including a ‘reply to’ address is good for your deliverability, as every time a subscriber replies to an email it is seen as a good signal by ISPs, which has a positive impact on your sender reputation.
Ideally your 'reply to' address would be an actively monitored inbox so that you can receive and action the replies you get.
‘firstname.lastname@example.org’ is the ‘reply to’ address, and all responses are sent to that email address.