====Blacklist service====
[[userguide:servermanagement|Server Management]] > [[userguide:servermanagement:networkservices|Network Services]] > [[userguide:email:emailsettings|Email]] > [[userguide:email:emailsettings#blacklisting|Blacklisting]] > Add / Modify

This form adds or edits **one** DNSBL used by the mail server. The list of services and the **DNSBL block threshold** live on the [[userguide:email:emailsettings#blacklisting|Email Server Settings — Blacklisting]] tab.

==Blacklist service==
Enter the fully-qualified host name of the DNSBL, for example ''zen.spamhaus.org'' or ''bl.spamcop.net''. Do not include ''http://'' or a trailing path.

==Defer Temporary==
If enabled and the blacklist **cannot be reached**, the mail server returns a **temporary error** so the sending server will retry later. If disabled, mail is accepted when the list is unreachable. This is the **Sendmail** behaviour. Postfix/Postscreen does not use this option the same way.

==Activate service==
Enable this DNSBL. Inactive entries stay in the GUI but are not queried.

==Weight==
Integer from **1** to **99**. Default is **1**.

When **Postscreen** queries this list and the connecting IP is listed, this weight is **added** to a score. Postscreen **rejects** the client only when that score is **greater than or equal to** the **DNSBL block threshold** on the Blacklisting tab.

Examples (Postfix/Postscreen):
  * One list, weight 1, threshold 1 — any listing blocks (simple recommended setup).
  * Three lists, each weight 1, threshold 2 — block only if at least two lists agree.
  * A trusted list with weight 3 and threshold 3 — a hit on that list alone is enough, even if other lists are also enabled.

Save returns to the Blacklisting tab.