Fun with new mailservers

I’m building a new set of mailservers for wordtothewise.com – our existing mailserver was “I’ll repurpose this test box for a week” about four years ago, so it’s long past time.
I tested our new smarthost by sending a test mail to gmail. This is the very first email this IP address has sent in at least three or four years, possibly forever:

host gmail-smtp-in.l.google.com[74.125.25.27] said:
421-4.7.0 [184.105.179.171      15] Our system has detected an unusual rate of
421-4.7.0 unsolicited mail originating from your IP address. To protect our
421-4.7.0 users from spam, mail sent from your IP address has been temporarily
421-4.7.0 rate limited. Please visit
421-4.7.0 http://www.google.com/mail/help/bulk_mail.html to review our Bulk
421 4.7.0 Email Senders Guidelines. u2si19966404pbz.202 – gsmtp (in reply to end of DATA command)

Sigh. IP warmup is hard.
I spun up our new MX and within three minutes, before I’d sent any test mail myself, I was seeing relay tests from the therichsheick spammer. Still scanning for open relays, still using the same Yahoo addresses. Followed immediately by someone else doing the same thing using gmail addresses.
 

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DMARC and organizations

Comcast recently published a statement on DMARC over on their postmaster page. The short version is that Comcast is publishing a DMARC record, but has no current intentions to publish a p=reject policy for Comcast user email. Comcast will be publishing a p=reject for some of their domains that they use exclusively to communicate with customers, like billing notices and security notices.
Comcast does point out that Yahoo! and AOL’s usage of p=reject is “not common usage.”
This is something a lot of people have been arguing loudly about on various mail operations lists and network lists. DMARC is about organizational identity. In fact, I was contacted about my DMARC primer and told that I didn’t mention that it’s not about domains, it’s about organizations.
The way I read the DMARC spec, it is all about organizational identity. The underlying theme being that the domain name is linked to a particular organization and everyone using email at that domain has some official relationship with that organization. I’ve always read the spec mentally replacing organization with corporate brand. This was for brands and organizations that strictly control how their domains are used, who can use those domains and how the mail is sent with those domains.
I never expected any mailbox provider or commercial ISP to publish a p=reject message as it would just break way too much of the way customers use email. And it did break a lot of legitimate and end user uses of email. Many organizations have had to scramble to update mailing list software to avoid bouncing users off the lists. Some of these upgrades have broken mailbox filters, forcing endusers to change how they manage their mailboxes.
Even organizations see challenges with a p=reject message and can have legitimate mail blocked. At M3AAWG 30 in San Francisco I was talking with some folks who have been actively deploying DMARC for organizations. From my point of view anyone who wants to publish a DMARC p=reject should spend at least 6 months monitoring DMARC failures to identify legitimate sources of email. The person I was talking to said he recommends a minimum of 12 months.
This is just an example of how difficult it is to capture all the legitimate sources of emails from a domain and effectively authenticate that mail. For a mailbox provider, I think it’s nearly impossible to capture all the legitimate uses of email and authenticate them.
It remains to be seen if the other mailbox providers imitate Yahoo! and AOL or if they push back against the use of DMARC reject policies at mailbox providers. Whatever the outcome, this is a significant shift in how email is used. And we’re all going to have to deal with the fallout of that.

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ReturnPath on DMARC+Yahoo

Over at ReturnPath Christine has an excellent non-technical summary of the DMARC+Yahoo situation, along with some solid recommendations for what actions you might take to avoid the operational problems it can cause.

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Why do we "warmup" IP addresses

IP address warmup is a big issue for anyone moving to a new IP address for sending.
I’m constantly being asked how to warm up an IP. My answer is always the same. There’s no right way to warm up an IP nor is there a specific formula that everyone should follow.
What warming up is about is introducing mail traffic to receiving spam filters in a way that lets the filter know this is a legitimate email stream. This means sending small but regular amounts of mail that recipients interact with. As the filters adjust to the amount of mail from that IP, more mail can be sent over that IP. Increase the mail volume over the next few weeks until the desired volume is reached.
There are a couple things to remember about warming up.

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