Inbox is a label to send email to, and an mailbox to respond from.
Alias is a label but no inbox to send from.
Forward is a bounce from one inbox to another.
Distribution List is an alias that act as a forward to route to a set collection of inbox’s.
An inbox will receive mail and send it… from that label. Rob@sample.ext can get email and send it from that label.
An alias is another label that routes to an inbox. Thedude@sample.ext can be an alias of rob@sample.ext. So if you send email to thedude@sample.ext it’ll get to the rob inbox; but thedude@sample.ext cannot send email. Only an inbox can do that; so emails will get responded to from rob@sample.ext
A forward will take a message going to an alias or inbox and send it to an external inbox. This could be with our without saving the message before sending it out.
If we continue to drill down on features…
A rule is a set of instructions that trigger inside the inbox. This could be a completely different set of forwards that happen once the email gets to the inbox. Most ‘account forwards’ will happen before the messages get to the inbox.