SEM-Fresh is a dynamic email blacklist maintained by Spam Eating Monkey (SEM), designed to flag newly registered domains that might be used for spam. Since a significant portion of spam originates from new domains, SEM-Fresh lists domains registered within the last 5 to 30 days. There are different categories within SEM-Fresh, such as SEM-FRESH5 (for domains registered in the past 5 days) and SEM-FRESH30 (for those registered in the past 30 days).

When your domain is flagged by SEM-Fresh, emails sent from it are more likely to land in recipients' spam folders, especially during the initial days of domain registration. This occurs because SEM assumes that recently registered domains may not yet have established a solid reputation and could potentially be used for spam.

Domains are automatically removed from SEM-Fresh after a specific number of days, depending on the category. For example, if your domain is listed in SEM-FRESH5, it will be removed after 5 days unless it continues to show suspicious behavior.

To mitigate the impact of being listed on SEM-Fresh, it's recommended to warm up your new domain by gradually increasing email activity, rather than sending bulk emails immediately after registering the domain. This helps build a positive reputation and avoid landing in spam​