Original sentence: Because of spam, it is becoming increasingly difficult to reliably forward mail across different servers, and some recommend to avoid it if at all possible.Email administrators sometimes use the term redirection as a synonym for server-based email-forwarding.That server can deliver a message to a user's mailbox and/or send it forward.The domain name (the part appearing to the right of @ in an email address) defines the target server.for that class of addresses.forward files (see below) provide a typical example of the implementation of server-based forwarding
Edited sentence: A domain may also define ; they have no mailboxes and forward messages without changing any part of their envelopes.Because of spam, it is becoming increasingly difficult to reliably forward mail across different domains, and some recommend to avoid it if at all possible.By contrast, primary servers can deliver a message to a user's mailbox and/or forward it by changing some envelope addresses.Email administrators sometimes use the term redirection as a synonym for server-based email-forwarding to different recipients.The domain name (the part appearing to the right of @ in an email address) defines the target server(s).for the corresponding class of addresses.forward files (see below) provide a typical example of server-based forwarding to different recipients