March 2016: The Month In Email

Happy April! I’m just back from the EEC conference in New Orleans, which was terrific. I wrote a quick post about a great session on content marketing, and I’ll have more to add about the rest of the conference over the next week or so. Stay tuned!
March2016_blog
Here’s a look at what caught our attention in March:
On the DMARC front, we noted that both Yahoo and mail.ru are moving forward with p=reject, and Steve offered some advice for ESPs and software developers on methods for handling this gracefully. I also answered an Ask Laura question about making the decision to publish DMARC. Look for more on that in this month’s Ask Laura questions…
Our other Ask Laura question this month was about changing ESPs, which senders do for many reasons. It’s useful to know that there will generally be some shifts in deliverability with any move. Different ESPs measure engagement in different ways, and other issues may arise in the transition, so it’s good to be aware of these if you’re contemplating a change.
In industry news, I wrote a sort of meta-post about how the Internet is hard (related: where do you stand on the great Internet vs. internet debate? Comment below!) and we saw several examples of that this month, including a privacy debacle at Florida State University. Marketing is hard, too. I revisited an old post about a fraud case where a woman sued Toyota over an email marketing “prank”. As always, my best practices recommendation for these sorts of things (and everything else!) really boils down to one thing: send wanted email.
Steve wrote extensively about SPF this month in two must-read posts, where he explained the SPF rule of ten and how to optimize your SPF records. He also wrote about Mutt, the much-loved command line email client, and marked the passing of industry pioneer Ray Tomlinson, who, in addition to his many accomplishments, was by all accounts a very thoughtful and generous man.
Finally, I occasionally like to take a moment and follow the twisty paths that lead to my spam folder. Here’s a look at how Ugg spams my email doppelganger, MRS LAURA CORBISHLEY. In other spam news, there’s a lot of very interesting data in the recent 10 Worst list from Spamhaus. Take a look if you haven’t seen it yet.

Don't mess with my email
Thoughts from #EEC16

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Optimize your SPF records

I talked on Monday about the SPF rule of ten and how it made it difficult for companies to use multiple services that send email on their behalf.
Today I’m going to look at how to fix things, by shrinking bloated SPF records. This is mostly aimed at those services who send email on their customers behalf and ask their customers to include an SPF record as that’s the biggest pain point, but some of it is also useful to people publishing their own SPF records.
email_vice
Get rid of costly SPF directives
First, rethink using the “mx” directive. It’s often used in example SPF records, because it makes them look simpler. But an MX directive always triggers a DNS lookup that counts against your limit of ten, and it’ll also trigger a DNS lookup for each hostname in your MX record – they don’t count against the SPF limit but may increase the latency of your delivery a little. Better than using “mx” is to use explicit “ip4” and “ip6” records to list the addresses your smarthost and MX send mail from. Even though this makes your SPF record look longer it’ll actually make it smaller, as measured by DNS queries, as a single “mx” directive costs more than 20 “ip4” directives.
Similarly, avoid the “a” directive. It’s much less commonly seen but again can usually be replaced with “ip4” or “ip6” directives.
Don’t use “ptr” directives. They’re deprecated by the current SPF RFC.
Check the address ranges
If you have many “ip4” and “ip6” directives, make sure they’re not redundant. Are there any address ranges that you’re not using any more? Are there any adjacent address ranges that can be merged? For example, “ip4:x.y.z.4/24” and “ip4:x.y.z.5/24” can be replaced with “ip4:x.y.z.4/23” (note that you can’t always replace adjacent address blocks of the same size – read up on CIDR notation).
If you’ve generated your CIDR blocks from address ranges you can sometimes have very inefficient representations. The address range 10.11.12.1-10.11.12.254 needs 14 “ip4” directives to represent precisely. Instead you can use the single directive “ip4:10.11.12.0/24”, even if you’re not sending any email from the .0 or .255 addresses.
You don’t need a “~all” or “-all” at the end of a TXT record that is only included in another SPF record, not used directly. It won’t do any harm but it wastes a few characters.
Once you’ve got your list of SPF directives cleaned up the next thing to do is to pack them into one or more DNS TXT records.
Use as few TXT records as you can
Some SPF tutorials say that you can’t put more than 255 characters of SPF data into each TXT record. That’s not quite true, though.
A TXT record contains one or more strings of text and each string can contain no more than 255 characters. But an SPF checker will take all of the strings in a TXT record and concatenate them together in order before it starts looking at the content. So you can have more than 255 characters of SPF data in a TXT record by splitting it into more than one string. (Some low-end DNS management web front ends don’t really understand TXT records and won’t let you include multiple strings – you should check that your DNS management system does before relying on this).
How much more than 255? That’s where you have to get a little familiar with the DNS protocol, as the real limitation is that you don’t want your DNS packets to be more than 512 bytes long. (Why 512 bytes? That’s a long story of protocol changes and incompatibility, but 512 bytes are about as big as you can reliably use over UDP. Just trust me.)
The DNS overhead for a reply that contains a single TXT record with two strings is about 34 bytes, plus the length of the hostname that’s being queries (e.g. “spf.example.com” is 15 bytes). So to keep within the 512 byte limit you need to break your SPF into chunks of no more than 478 minus the length of the hostname. Then you need to break that SPF data into two strings (remembering that they’ll be concatenated with no white space added, so if you break it at a space you need to include the space at the end of the first string or the beginning of the second).
That’ll give you a TXT record that looks something like this:

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September 2015: The month in email

September’s big adventure was our trip to Stockholm, where I gave the keynote address at the APSIS Conference (Look for a wrapup post with beautiful photos of palaces soon!) and had lots of interesting conversations about all things email-related.
Now that we’re back, we’re working with clients as they prepare for the holiday mailing season. We wrote a post on why it’s so important to make sure you’ve optimized your deliverability strategy and resolved any open issues well in advance of your sends. Steve covered some similar territory in his post “Outrunning the Bear”. If you haven’t started planning, start now. If you need some help, give us a call.
In that post, we talked a bit about the increased volumes of both marketing and transactional email during the holiday season, and I did a followup post this week about how transactional email is defined — or not — both by practice and by law. I also wrote a bit about reputation and once again emphasized that sending mail people actually want is really the only strategy that can work in the long term.
While we were gone, I got a lot of spam, including a depressing amount of what I call “legitimate spam” — not just porn and pharmaceuticals, but legitimate companies with appalling address acquisition and sending strategies. I also wrote about spamtraps again (bookmark this post if you need more information on spamtraps, as I linked to several previous discussions we’ve had on the subject) and how we need to start viewing them as symptoms of larger list problems, not something that, once eradicated, means a list is healthy. I also posted about Jan Schaumann’s survey on internet operations, and how this relates to the larger discussions we’ve had on the power of systems administrators to manage mail (see Meri’s excellent post here<).
I wrote about privacy and tracking online and how it’s shifted over the past two decades. With marketers collecting and tracking more and more data, including personally-identifiable information (PII), the risks of organizational doxxing are significant. Moreso than ever before, marketers need to be aware of security issues. On the topic of security and cybercrime, Steve posted about two factor authentication, and how companies might consider providing incentives for customers to adopt this model.

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Prepping for EEC


Tomorrow I head off to New Orleans to the EEC conference. It’s my first one and I’m really looking forward to meeting some of the people I only know online.
I’ll be speaking on two panels on Friday:
All You Ever Wanted to Know about Deliverability (But Were Afraid to Ask) at 10:50. This is your chance to ask those questions of myself and other experts in the field. I always enjoy Q&A panels and actually hearing from folks what their big deliverability questions are. (and remember, if you have a question, you can always send one to me for Ask Laura)
and the closing Keynote panel
ISP Postmasters & Blacklist Operators: Defending Consumer Inboxes at 1:10. I’m on a panel with various ISP postmasters, blacklist operators and we’ll be talking about what it’s like dealing with the deluge of mail. For instance, there is a huge outbreak of bot-spam at the moment, and a lot of the filters are struggling to keep up. In fact, I’m a last minute replacement for one filter company as they are in all-hands-on-deck firefighting mode to keep their customers safe.
Hope to see you there!
 

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