The numbers:

• Since December 23rd I’ve received 1,740 Spam e-mails that were stopped by the Pobox.com spam filters.
• Pobox.com stopped three e-mails that I released. These released e-mails were all bulk e-mails and I released them si I could unsubscribe, technically they weren’t spam. Pobox.com no longer receives “real” e-mails for me other than long forgotten mailing lists, so this isn’t an accurate measurement of how well it avoids false positives. I have Pobox.com set to use “Standard Settings” for the spam filter and I allow it to automatically update my anti spam actions which are the defaults.
• GMail stopped an additional 4 spam e-mails that Pobox.com let through.
• GMail stopped 100 spam e-mails that were sent directly to it (not the Pobox forwarded e-mails).
• GMail didn’t have many opportunities for false positives when identifying Spam. It only had problems when dealing with my Pobox.com discard reports. It let about 1/2 of the discard reports through while identifying the others as spam. The inconsistency seems to be due to the specific server that GMail got the message from as the sending server for the ones flagged as spam was different than the ones for messages that got through. (The sending address is not in my contact list which would probably avoid the whole issue.)
• On the Apple Mail Client side 5 e-mails that got through were incorrectly flagged as junk (spam). All were from bulk e-mailers and none were in my address book or previous recipients list.
• My daily count hit a low of 36 on Jan 2nd, but it picked right up and my daily high was 92 on Jan 9th. (Those highs/lows are since Dec 23rd.

That’s all for now, just a quick update to the numbers.

The only two places spam arrives directly from the internet are at my email forwarder and GMail.

GMail
Gmail (Google Mail) received 18 Spam e-mails over 5 days. There were not any false positives and no spam got through.

Pobox – Mail Forwarder
My mail forwarding service, pobox.com, flagged and held 339 emails as spam over a 5 day period. The only false positives were from one sender. It was an bulk advertising e-mail, but from a place I’d done business with. I could have added the sender to the whitelist, but I chose to unsubscribe instead.

As has been mentioned, ISPs handle email differently when it’s from a forwarder than they do when it’s direct. The three accounts the mail is being forwarded to only receive email from the forwarder. (The .Mac account gets a few e-mails from Apple and the Yahoo account gets a few e-mails from Yahoo.) If my email forwarder didn’t detect a message as spam it passed it along. I had the e-mails sent to my Yahoo, .Mac and AOL (“My eAddress”) accounts.

Yahoo
I reset the junk filter when I started. As I checked the mail each day I used Yahoo’s junk mail button to properly mark the e-mail and train the filter. Only e-mail not caught by the forwarder was sent to Yahoo.

The first day Yahoo missed 10 out of 11 junk e-mails. But even with just these e-mails as training it started catching more than it missed from that point on. During the 5 day period Yahoo caught 19 junk emails and let 17 through.

There was one false positive which was a marketing e-mail which I added to my address book for future delivery.

There was another marketing email where the exact same email was sent to two of my email addresses. Yahoo saw one as junk but not the other. I’m guessing it was the second one that if flagged as junk rather than an inconsistency.

.MAC Mail
.Mac mail does not have any web based spam filter, at least not visible to the user.Typically, only 1/2 the junk email appeared in my mailbox. One of the undelivered emails was a daily report I receive. I added the sender address to my address book on my Mac. From that point on these emails were received. I do sync my address book with .Mac.

AOL (My eAddress)
Over the 5 day period AOL flagged 21 emails as junk and let 31 go through. The first day is the only time it caught more than it let through. It performed worse as it was trained. There weren’t any false positives. AOL seems to be applying its own filter before delivering the mail as the number of emails received in my AOL box was less than the number delivered to Yahoo.

Apple Mail
I used Apple mail to read mail delivered to my .Mac account. The first day Apple Mail caught 10 and missed 10 junk mails. After that initial training it improved dramatically catching 6 and missing 1.

Apple mail also flagged 5 emails as junk which were not. Not all of these were bulk emails. Two were transaction receipts or info requests sent directly to me. But it’s almost a given that they were sent using an automated system that handles a large volume.

As a test, after delivery of the mail from .Mac mail I downloaded mail from Yahoo. This would duplicate the mail received from .Mac mail. Mail that had been marked as junk or not junk when received from .Mac mail was properly processed.

Thunderbird
Thunderbird had the slowest junk mail filter to train. It also requires marking both junk and non-junk mail to train it. As a small, unscientific test I tried just marking junk for the firs couple of days. The filter made no real improvement despite a large volume of junk. I reset the filter and started marking every email received as either junk or not junk. There was a noticeable improvement right away. The first two days it missed everything, the last two days it caught everything. Thunderbird had 1 false positive which was a bulk email, the same sender that I had to add to my Yahoo address book to let through. For Thunderbird I marked it not junk and added the sender to my “Collected Addresses”.

Thunderbird on Windows handled the junk email the same way it did on Mac. I used the same emails for training.

Outlook Express
I looked at Outlook Express on Windows XP SP2. The only junk mail tool is a blocked address list.

Next Week
Ideally what I want is for all mail to be delivered to my desktop inbox and let it filter for junk mail. This keeps me from having to go to another location to look for blocked email that I actually need.

I turned off the spam filters at my email forwarder and at Yahoo. This week we’ll see how well Thunderbird and Apple Mail handle the spam.