Does email have a guarantee of delivery?

A client asked me earlier this week what SLAs ISPs provided for email delivery. The short answer is that there isn’t a SLA and that the only guarantee is that the email will get there when it gets there.
But as I was mentioning this to Steve, he pointed out that there was a recent change in the RFCs for email. In both RFC 821/2 and RFC 2821/2 (the original email related RFCs and the update in the early 2000’s) the RFCs stated that once a receiving MTA accepted an email that that MTA was required to either delivery the mail or generate an asynchronous bounce. While this isn’t a standard SLA, it does mean that a 2xy response after DATA meant the email would either be delivered to the user or be sent back to the sender. Despite the RFC requirements some receivers would still drop mail on the floor for various reasons, sometimes intentionally and sometimes not.
RFC 5321/2, the current SMTP standard, still says that once a server accepts the mail it must not lose that mail ‘for frivolous reasons.’ The RFC goes on to admit, though, that in recent years, SMTP servers are under a range of attacks and dropping mail on the floor is not frivolous in those cases.
 

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Emails that make you smile

This summer’s non-work project for me has been training for a 5K run with Fleet Feet in Menlo Park. As part of the training programs we get weekly emails from the store on Monday. As I was reading through today’s email, I found myself smiling and happy. Lisa, who is one of the store owners and writes the emails, is just so happy and bouncy and thrilled to share her love of running and that comes through in the newsletter.
Our group’s primary coach is the other store owner. During runs we often talk about random stuff, and when I tell people I do email delivery, they always start talking about their experience with email and spam. One night I was running with Jim, and we were talking about Jim’s experiences with sending email. He mentioned their ESP and talked about how convenient it was. But then he mentioned he wasn’t sure that they were sending enough mail (which made me laugh hard enough I almost tripped on a curb).
I realized I am not just a delivery expert when I started thinking about all the ways they could increase the amount of email they send, while still maintaining the quality and the friendly feel of their bulk emails. What could they offer local runners that would increase the value of the store to them? The first very obvious thing was a race calendar. There are dozens of local races every week, telling folks about upcoming races and entry deadlines would be a way to contact folks regularly without it always being a “buy stuff from us!!”
What commercial emails have you gotten recently that have made you smile?

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The Physics of the Email Universe

We talk a lot about rules and best practices in email, but we’re mostly talking about “squishy” rules-of-thumb that are based on simplified models of how mail systems, spam filters, recipients, postmasters and blacklist operators behave. They’re the biology, ecology and sociology of the email ecosystem.
There’s another set of rules we tend to only mention in passing, if at all, though. They’re the steely, sharp-edged laws that control the email universe. They’re the RFCs that define how email works and make sure that mail systems written by hundreds of different people across the globe all work and all interoperate with each other.
Building a message from Zeros and Ones
RFC 5322 – Internet Message Format
This tells you everything you need to know about crafting a simple email, with a subject line, a sender, some recipients and a simple plain-text message. It’s also the foundation of all fancier emails. If you’re creating emails, this is where to start.
A little more than plain ASCII
RFC 2047 – MIME Part 3: Message Header Extensions for Non-ASCII Text
RFC 2047 is one small part of the MIME (Multipurpose Internet Mail Extensions) suite of protocols that allow you to include pictures and attachments and prettily formatted text and comic sans in your email. This part defines how you can put things other than the plainest of plain text in your subject lines or in the “friendly from” of your message. It’s what allows you to put Hiragana, or Cyrillic, or umlauts, or cedillas, or properly matched double quotes in your subject line. It also let’s you put hearts or smiley faces or other little pictograms there – but nothing this useful is going to be perfect.
RFC 2045 – MIME Part 1: Format of Internet Message Bodies
This shows how to send an image, or a plain text mail in a different character set, or an HTML mail. It doesn’t tell you how to send plain text and HTML, or to send HTML with embedded images, or a message with an attached document. For that you need…
Finally, Modern Email
RFC 2046 – MIME Part 2: Media Types
This builds on RFC 2045 to allow you to have many different chunks in a message – this is what you need if you want to send “proper” HTML mail with a plain text alternative, or if you want embedded images or attachments.
Getting From A To B
RFC 5321 – Simple Mail Transfer Protocol
A message isn’t much use unless you send it somewhere. RFC 5321 explains the mysteries of actually sending that message over the wire to the recipient. If you need to know about the different phases of a message delivery, what “4xx” and “5xx” actually mean, why there’s not really any such thing as a hard or soft bounce defined, just temporary or permanent failures, or anything else about actually sending mail or diagnosing mail delivery, this is your starting point.
The Rest Of The Iceberg
I’ve only touched on the very smallest tip of the email iceberg here. There’s much, much more – both in RFCs and ad-hoc non-RFC standards. If you’re interested in more, this is a decent place to start.

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Deliverability of Facebook.com email addresses

Christopher Penn at What Counts did some testing to see what delivery to Facebook.com addresses looks like. It looks pretty grim.
 

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