mxm Imap Client (2.0.1)

It stores message headers in a fast local cache in Zope, but not the message body. Whenever a message is viewed, it is fetched from the Imap server.

This approach has the following advantages:

• Browsing messages is as least as fast as the Zope server, as new message headers are only fetched once in a while. This can be especially important if there is a slow line between the Imap and the Zope server. Many mail users have several thousand messages in their mailboxes. It can be a drag to fetch them all from the server if headers are not cached locally.
• It compares the cached message headers with the messages on the server, making it possible to only fetch headers for changed/new messages. Minimizing traffic between server and client.
• Leaving the message body on the Imap server, means that attachments also stays, so that you don't need to bloat the ZODB with thousand of multi- megabyte files.
• Message subjects can be searched on the client
• Making interface changes is simple for Plone developers, as they mostly work with normal Plone folders and content objects. They also don't need to know about special Imap formats.

There is also some disadvantages

• Fetching a message uses up one zope thread, so if many people are fetching large messages at the same time, on slow servers, it can bring your server to a halt.

It is possible though to set up a batch job to fetch new message headers so that only one thread is used for that at a time.