The characteristics of a communications account are used to determine whether the account is being used by a spammer. When the account is being used by a spammer, the use of the account for outgoing communications is limited to help prevent spam from being sent from the account. For example, communications from the account can be blocked, messages from the account may be delivered to a spam folder at the recipient (rather than an "inbox"), or outgoing messages from the account may be rate-limited.