Reputation in email marketing is the degree of trust that people have toward the sender.
When the sender has a good reputation, there is a significantly higher chance that the sender’s mailings will get through to recipients’ Inboxes. If the sender has a poor reputation, these mailings are likely to end up in the Spam folder.
All well-known mailing services, as a rule, have good reputations. To manage their reputations, they must effectively prevent spam from going out through their systems and block any suspicious accounts.