= Custom IMAP processing
:navtitle: Custom IMAP processing

James allows defining your own handler packages.

An Imap package is a simple class that bundles IMAP processing components:

....
public interface ImapPackage {
    Collection<ClassName> processors();

    Collection<ClassName> decoders();

    Collection<ClassName> encoders();
}
....

Processors needs to be of class `AbstractProcessor`, decoders of class `AbstractImapCommandParser`
and encoders of class `ImapResponseEncoder`. Extensions-jar mechanism can be used to load custom classes.

Custom configuration can be obtained through `ImapConfiguration` class via the `getCustomProperties` method.

A full working example is available link:https://github.com/apache/james-project/tree/master/examples/custom-imap[here].

See this page for xref:imap.adoc#_extending_imap[more details on configuring IMAP extensions].

== IMAP additional Connection Checks

James allows defining your own additional connection checks to guarantee that the connecting IP is secured.

A custom connection check should implement the following functional interface:
```
@FunctionalInterface
public interface ConnectionCheck {
    Publisher<Void> validate(InetSocketAddress remoteAddress);
}
```

- `validate` method is used to check the connecting IP is secured.

Then the custom defined ConnectionCheck can be added in `imapserver.xml` file:
```
<additionalConnectionChecks>org.apache.james.CrowdsecImapConnectionCheck</additionalConnectionChecks>
```

An example for configuration is available link:https://github.com/apache/james-project/blob/master/third-party/crowdsec/sample-configuration/imapserver.xml[here].