Me I prefer the pro-active approach of MailWasher Pro, which is operating outside/independent of your email client, so it doesn't really matter which one it is. You first check for email using MailWasher, it doesn't download the complete email to do its analysis, it only downloads the headers, a small part of the body, it doesn't download images or attachments and it views what is downloaded in text only.
What is considered spam is flagged either by the program or you, you then click Process email, etc. and it deletes the flagged spam from the email server and the calls your email client, where you then download the remaining clean/non-spam email.