Email client for large mailboxes?
I am looking for a email client with the following features...
1. Supports both POP3 and IMAP;
2. Successfully handles multiple POP3 accounts to separate folders (at least 30);
3. Can handle large mailboxes (currently at approximately 12000 retained messages);
4. Thorough rules engine; and,
5. Stable enough to bet the bank on (or as close as possible).
I initially started looking at Thunderbird due to its cross-platform abilities however I have seen many negative threads relating to "large mailboxes" and speed issues. I am not sure what constitutes a "large mailbox" however, reliability is critical.
Thank you, in advance.