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Postmarking is a new part of the Outlook 2007 junk e-mail feature; it complements the existing feature set to reduce the amount of spam in your inbox.
One of the great advantages of e-mail is that it is easy and cheap to send. Unfortunately, this is the very same reason that makes it so useful to spammers as it enables them to send huge amounts of email in bulk.
Think of Postmarking as computational “postage” imposed when sending email. This is a small burden for an individual user, but is a very large burden for spammers. Spammers rely on being able to send thousands of mails per hour, and in order to be able to send spam with postmarking turned on, they would have to invest a very large amount of money to expand their computational power.
Postmarking generation is only present in Outlook 2007 and postmark validation is present in Outlook 2007, Windows Live Mail , Exchange 2007, and Windows Mail in Vista.
So, how does it work?
Sending e-mail with postmark: Before messages leave your Outbox, Office Outlook 2007 stamps each message with an e-mail postmark. The postmark incorporates unique characteristics of the message, including the list of recipients and the time when the message was sent, making the postmark valid only for that message. As a result it takes a little longer for the message to leave the Outbox – however, this is not noticeable during normal day-to-day Outlook usage.
Receiving e-mail with a postmark: When a recipient e-mail application that supports Outlook e-mail postmarking receives postmarked mail, it recognizes the postmark. The postmark means that the message is most likely not spam and this is an additional factor evaluated by the junk e-mail filter when determining if an email is spam or not.
How to turn Postmarking off
To turn on/off Postmarking, use the following option in Outlook 2007:
1. On the Tools menu, click Options.
2. On the Preferences tab, under E-mail, click Junk E-mail.
3. Clear the When sending e-mail, postmark the message to help recipient e-mail programs distinguish regular e-mail from junk e-mail check box.
Alessio RoicOutlook Program Manager
I am very glad to see something like this, but unfortunately a lot of my contact not use Outlook 2007, Windows Live Mail , Exchange 2007, or Windows Mail in Vista.
My dream is that MS, Google, Yahoo, AIM,... get together and make some thought about "anti spam" together, an additional filter only for some applications make not really sense. :-/
Post Update Notification Text change: "How to turn postmarking on" to "How to turn postmarking off". Thanks! -michael affronti
outlook program manager
I've sent some test messages from my Outlook 2007 client through Exchange 2007 to my gmail account and when viewing the source I don't see any sort of data in the SMTP source (post marking is enabled on my OL 2007 client). Is this intra-oranizational only (i.e. is the postmark stripped when leaving the Exchange environment)?
I figured it out. So you have to have the Junk Mail feature enabled from low to safe list only for this feature to work. Otherwise it doesnt apply the x-cr-puzzleid and x-cr-hashedpuzzle to the message. This being the case, shouldn't the post marking feature be greyed out if the Junk Mail feature is not enabled? Seems this is a tad confusing and would lead people to a false sense of security.
Thanks for your message. I would like to clarify how postmarking works. In Outlook 2007 postmarking generation is separate from the junk e-mail filtering feature. Therefore when the junk e-mail protection is set to “No automatic filtering” the outgoing e-mails still get postmarked by Outlook. However, since the Junk E-mail is not enabled, incoming messages are not moved to the Junk E-mail folder automatically. Thanks Alessio Roic
Outlook Program Manager
How does this compare to Yahoo's DomainKeys, or to the recent IETF draft-approved DKIM?
"Your message did not reach some or all of the intended recipients." I keeping getting this message on all my out going mail, what should I do? Gary
Please could you make interoperability libraries available for this feature. It needs to be possible to validate these headers in other MUAs and especially in CRM systems, otherwise their usefulness is extremely limited.
I've had clients not able to send attachments and found the postmarking header info on our firewall as being a 'long header'. We use Exchange 5.5, which seems to not like the messages either. Is there anything we should watch for people using this feature that are getting kicked back emails from ISPs? Thanks.
Have Microsoft really no better ideas like this?
Why still use a 25 year old SMTP/POP3 portocol?
It appears this feature was removed from Outlook 2010.
This is a nice feature, however I would say there are some issues with the way the hash is generated. Due to the randomness of creation, I am having email from my users blocked sometimes due to our content management systems blocking outbound profanity. (We are in customer service) What happens, is the x-cr-hashedpuzzle generates its string of text and ends up occasionally coming up with profane words. The latest one today being the word F****ck which sends me some interesting content management alerts. My suggestion would be to release a patch possibly containing a list of certain words / phrases to avoid in the creation of the hash, otherwise systems using content management but not yet moving to Outlook 2010 are going to repeatedly run into this issue.