When it was set to 127.0.0.1, I did not receive my email messages.
Tried what Bob posted...
You should have C:\...\Avast4\ashMaiSv.exe running in your computer (it's the email scanner). You could check clicking Ctrl+alt+del
After I changed it back, I got today's messaages, but I did not receive my missing messages from the previous 4 days.
Well, if avast could not scan the messages, of course, avast could never 'delete' them.
It should be a problem of your ISP or even your email client.
avast! does not have a spam module and only delete infected messages if you said so (the automatically deletion is only available on Professional version).