Word to the Wise

We make email better.


We make email better.

Word to the Wise helps email marketers create more effective email messages, programs and infrastructures. We advise you how to skillfully navigate the constant business, technology, and policy challenges so your messages reach your customers.

We can help you with your email strategy, deliverability challenges and many other email issues.

Latest stories

C is for Cookie


Trekkie Monster. He’s obsessed by social media and isn’t owned by Children’s Television Workshop. What is a Cookie? I’m not talking about biscuits, nor about web cookies, at least not exactly. When you’re talking to a protocol developer a cookie is a thing you’re given, that you hang on to for a while, then give back. If you leave your suitcase with your hotel...

Unresolvable RFC.5321 domain at Yahoo


Seen this recently? 451 Message temporarily deferred due to unresolvable RFC.5321 from domain; see This is Yahoo doing some extra work to identify that the 5321.From domain1The return-path, aka the 821.From, 5321.From, or bounce address is the email address you send from at the protocol level, not the email address in the From: header, and it’s the address any bounces will be sent to. of...

Is .edu a canary?


Several times recently I’ve heard about something unusual happening email delivery-wise at academic domains that was new, and wasn’t being seen at non-academic domains on the same lists. Most recently it was aggressive following of all links in an email at delivery time, seen at several .edu domains, all using the same mail provider. Not that unusual a thing in itself, we know that...

Want a link on WttW?


There is an ever increasing amount of spam I am getting from various companies asking for links here on WttW. The Answer is No. We do not have paid links. We do not have sponsored posts. Any links on the site are done at our whim and because we have something to say about your company. The only place we offer links is on the ESPs and Purchased Lists post. And, I gotta tell you, if you buy my...

Is email dead?


These last few years have been something, huh? Something had to give and, in my case, that something was blogging. There were a number of reasons I stopped writing here, many of them personal, some of them more global. I will admit, I was (and still am a little) burned out as it seemed I was saying and writing the same things I’d been saying and writing for more than a decade. Taking time...

“Friendly From” addresses


When we’re looking at the technical details of email addresses there are two quite different contexts we talk about. One is an “821 address” or “5321 address”. This is the email address as it’s used by the SMTP protocol, as part of the “MAIL FROM: <>” or “RCPT TO: <>” commands sent to the mailserver. It’s defined in RFC 821...

Don’t break the (RFC) rules


It looks like Microsoft are getting pickier about email address syntax, rejecting mail that uses illegal address formats. That might be what’s causing that “550 5.6.0 CAT.InvalidContent.Exception: DataSourceOperationException, proxyAddress: prefix not supported – ; cannot handle content of message” rejection. Why do we care? It’s good to send syntactically valid...

Life of an Email


I’m repeating the presentation I gave at M3AAWG in London for the Certified Senders Alliance.It’s all about how to send an email by hand, and how knowing the mechanics of how an email is sent can help us diagnose email delivery issues.We’re starting in about five hours from when I post this.Register at

Gmail Program for Election Mail


A few months ago, Google made a splash in the political press and the email marketing space when they asked the FEC the following question: May Google launch a free and non-partisan pilot program to test Gmail design features, which will be open to authorized candidate committees, political party committees, and leadership political action committees, where spam detection as applied to messages...

Confidential to ESPs


Dear Colleagues at ESPs, We have a problem. More specifically, YOU have a problem. You have a spam problem. One that you’re not taking care of in any way, shape or form. There was a point where ESPs started caring about spam out of their networks. They got blocked enough they had to take action. Because they took action a lot of the big blocklists started being nice. Spamhaus, for instance...

Recent Posts


Follow Us