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# Performance tuning

If you're running a busy mail server (many inbound/outbound emails every day), you can follow below suggestions for better performance.

### Setup a DNS server in LAN or localhost to cache DNS queries

Mail services heavily rely on DNS service and perform many many DNS queries, a cache DNS server in LAN or localhost helps A LOT:

- It speeds up DNS queries. This helps a lot to speed up mail flow.
- It reduces DNS queries to DNSBL servers, so that you can continue using their excellent service without exceeding the max query limit.

### Enable postscreen service to help reduce spam

- Enable postscreen service

If you don't want to use postscreen service, you can enable DNSBL service instead, it helps a lot too. Although both `postscreen` and pure DNSBL services uses the same DNSBL servers, but `postscreen` offers additional solutions to reduce spam, so postscreen is better.

postscreen and DNSBL service help catch a lot spam before putting the spams in local mail queue, so they save much system resource.

### Update Amavisd + Postfix config files to process more emails concurrently

- Process more emails concurrently