Hello Neville,
Take a look again. I was so impressed with the screen shots that I decided to download popper myself. It sends and recieves emails. There is also a user forum at the popper web site. I had a problem with popper (actually my PHP.INI setup) and recieved a helpfull answer from the programmer the next day. Not bad. And the program has almost all the functions you need apart from the spam filter. Here is the description from the web site: http://ractive.ch/popper/about.php
Popper is a Web based mail client that allows you to access your personal mailboxes on POP3 servers.
This means that you can access (read/answer) your mails from any browser. The difference to other web-mail services like hotmail etc. is, that you can access your mailboxes on POP3 servers.
Normally you use a program like Outlook, KMail, Netscape Messenger, Eudora etc. to access these mailboxes. Problems arise when you want to read your mails somewhere else then at home. Think about vacation :-).
This is where popper can help you. It gives you the possibility to read your mails from (almost ;-) any browser from anywhere... It even brings your read mails and your personal addressbook in your browser
Popper is a fully features mail-client that is (more or less) MIME-conformant. This means that you can open and save attachments, view HTML mails (although it's a bad habit to send those), view attached mails etc.
Replying, forwarding etc. is just as easy as with any other mail-client.
popper is written with PHP4 and is 100% java-free which reduces portability problem. You can even use lynx to read your mails ;-)
A small overview of the possibilities provided by popper:
Fetching mails from multiple POP3 servers
Reply and forward incoming mails
Compose new messages
Addressbook
View and send attachments
View HTML mails
Support of message-notification-disposition
Multiple languages (is your language missing?)
Configurable user interface
SPAM blocker
Calendar
more to come...
So you see. It is basically what your looking for and the work put into the program will definately save you masses of time programming.
Good luck,
Scott