One of the major features of Eudora is that you can right click on a message and it will allow you to change the server status of the message (Leave, Fetch, Delete, Fetch then Delete). Additionally, their filters allow you to automatically change the status based on filter settings. This is particularly useful if you want to remove spam from a server, but leave the good messages. The absence of this feature is one that is preventing me from switching from Eudora to Mozilla mail.

MASS-CHANGE: This bug report is registered in the SeaMonkey product, but has been without a comment since the inception of the SeaMonkey project. This means that it was logged against the old Mozilla suite and we cannot determine that it's still valid for the current SeaMonkey suite. Because of this, we are setting it to an UNCONFIRMED state. If you can confirm that this report still applies to current SeaMonkey 2.x nightly builds, please set it back to the NEW state along with a comment on how you reproduced it on what Build ID, or if it's an enhancement request, why it's still worth implementing and in what way. If you can confirm that the report doesn't apply to current SeaMonkey 2.x nightly builds, please set it to the appropriate RESOLVED state (WORKSFORME, INVALID, WONTFIX, or similar). If no action happens within the next few months, we move this bug report to an EXPIRED state. Query tag for this change: mass-UNCONFIRM-20090614