Confident Clean a Hacked Site Workshop Join me July 16th for this 90 Minute Workshop  Claim your spot

Lessons learnt migrating from Mailchimp to Buttondown


So I rather blew it. As part of the move to the new look site I took the opportunity to move from MailChimp to Buttondown for my newsletter. However things did not go according to plan…

This turned out to be a bit of a journey with some interesting lessons that I thought were worth documenting.

Let’s start at the begining:

I chose Buttondown as it came recommended by my friend Dave Smyth from Work Notes; he had recently migrated his own list over. Some googling and general checking out and it seemed to be a good fit for me. Simple email service that allowed me to just write emails.

A small independent with a privacy focus, It’s not perfect, the documentation is in Notion and some of the interface is probably best described as intentionally minimal.

Migration from MailChimp

The migration from MailChimp was actually a pretty painless exercise. If anything, I would argue the onboarding is easier than the migration between Tiny Letter and MailChimp, a process I had done earlier that year.

From within MailChimp I spent a few minutes fighting its UI but eventually worked out how to download my audience. Then it was a case of uploading them to Buttondown.

OK, this was particularly easy – win to Buttondown!

Setting up Buttondown

OK, so Buttondown is not complicated but it does have settings in multiple locations and I will be honest. not all of them are very logical to me. Some options are “Premium” as well and the GUI doesn’t really do much to help you work out what is what, barring the occasional tool tip.

One set of settings is the ability to specify which email you want the email to be sent from. This aids in deliverability, tick

So now we need to set some DNS, and a little bit of the magic is revealed, as, well, Buttondown is a GUI wrapper for Mailgun under the hood, as the DNS records we are pointing to are all Mailgun related.

This is a good thing, sending email is HARD. I don’t want someone trying to do it, so I am much happier knowing a specialist company is doing the hard work. However, I can’t help but think if it was my project I would have put those DNS records under my vanity nameservers, even if I just forwarded on all requests. As now, should Buttondown try to migrate to a different mail provider (or branch to multiple) we do have a bit of an issue, and lots of DNS records will need updating.

Long term I see a potential painful “upgrade” is going to be needed.

One of the DNS changes needed was to create a CNAME note “email” not “mail”, I will skip over how long it took me to notice I had pointed to “mail” by accident. Basically the is a CNAME to


; <<>> DiG 9.10.6 <<>>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24929
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

; EDNS: version: 0, flags:; udp: 512
;        IN    A

;; ANSWER SECTION:    180    IN    CNAME        60    IN    A        60    IN    A

;; Query time: 15 msec
;; WHEN: Mon Dec 07 18:00:21 GMT 2020
;; MSG SIZE  rcvd: 105

confirms it was set up correctly. OK, so I will admit at this point I only did a dig, I made no HTTP request, I was in my head sorting some DNS bits out. At this stage an alarm bell should have been ringing in my head.

However, it, and the other records such as SPF, all set up and confirmed both by me and Buttondown interface, we are good to go.

Writing the first email

So I write the email in MarkText then paste it into a Google Doc, for Babs to edit, just like this post. Then I copy and paste back out into the mail client, in this case Buttondown, and fix any weird foibles that might occur. With MailChimp this was a nightmare as Google Docs and MailChimp both tried to be clever, so it was nice to just be able to straight copy and paste and the markdown be automatically added. Generally it looked OK. I deliberately didn’t play too much with making things fancy, I figured I wanted to build such functionality up and I also wanted to experiment with the plainer looking email. What I did do is test! I sent myself 5 separate preview emails which I checked on:

  • Gmail Web Client
  • Android Gmail App
  • K9Mail a Android App
  • Apple Mail

Each time I was checking things like DO THE LINKS WORK and they did!

OK, time to send an email. It was at this point I found tags, as, until then, I hadn’t actually realised I could tag users. This would be useful later, and would have been really useful earlier.

Anyway, I hit send immediately and off went the email to my inbox.

I checked my inbox, sure enough there was an email!

  • Deliverability tick

Happy it had sent, I started stabbing around and realised the analytics were a little more complete then I was expecting. After all I had set up so I wouldn’t be collecting such stats.

It’s OK,I thought, it’s probably a bit of an interface bug.

Then I got a Tweet…

That’s strange, why would Claire be having issues? Of course my first thought was there was an issue with my site and I jumped to the Ransomware Article. OK, so there is no issue with the site itself, phew!

On opening the email that had been sent to me, I clicked on the Ransomware post and, yep, I had an identical issue!

Looking at the link:

Hmmm OK, that apparently is a tracking URL. My first thought was that the domain is not working properly so I quickly CURL’d the response

curl -I
HTTP/1.1 302 FOUND
Content-Length: 383
Content-Type: text/html; charset=utf-8
Date: Tue, 08 Dec 2020 20:19:11 GMT
Server: nginx
Connection: keep-alive

OK, so that is hitting that domain and is apparently working, but it doesn’t in the browser. By now I had already worked out why, but just to be sure I did:

curl -I
curl: (7) Failed to connect to port 443: Connection refused

Spot the difference?

Over HTTPS that url is failing to connect, but what is causing the insecure connection to be upgraded?

HTTP Strict Transport Header

The HTTP Strict Transport Header (HSTS) is a special Header sent by a server (in this case mine, or more specfically Netlify on my main domain) to say only try to connect over HTTPS. The first time a browser tries to connect it can do it over HTTP or HTTPS but then it’s presented with this header in the first response and from then on, if a browser gets a HTTP link for the site it will automatically jump to using HTTPS version.

So my site ( has the HSTS header set that looks like this:

strict-transport-security: max-age=31536000; includeSubDomains; preload

This basically say that you should always come to this site over HTTPS:

  • For the next year max-age
  • This policy includes Subdomains includeSubDomains so that means it effects
  • And that where possible it should be preloaded by browser preload

In addition my site is registered with, a website run by Google that allows sites that meet the conditions (basically the above configuration) to request that they are preloaded into Chrome and other Browsers. Meaning the browser will use the HTTPS version only, even if it’s never visited the site before.

So now we have a problem:

the subdomain was running over HTTP but not HTTPS but virtually every visitor would have a browser saying it knows NOT to run any subdomain over HTTP and to only go over HTTPS. So all the tracking URLs are broken, which means all the links in my newsletter are broken.


BUT BUT BUT, I checked this!

OK, slightly panicking I checked this. All the links were working in the preview, why?

Going back to the preview emails, and checking the links, the preview email links were not going through the domain. Presumably to stop issues where they get caught up in tracking!

But why was it tracking? I didn’t want it tracking. Glancing at the analytics I had some tracking information (presumably from email apps, rather than browsers) .

OK, so the issue appears to be the tracking, the tracking I don’t want.

How do I turn the tracking off? When you are doing things in a bit of a hurry you get grumpy. I was quite grumpy when I eventually tracked down the tickbox for:

Would you like to opt out of analytics? YES!

Ok so I have opt-ed out, now how to test, as when I tested previously I couldn’t see this issue as it wasn’t including the tracking links.

Buttondown tags

Tags seemed like the answer, and actually this is where simplicity really did win, and is one of the reasons I still really like Buttondown. I was able to generate a TEST tag, attach it to a single user and then send the email again by using the “reuse” option to resend. Except you have to change at least something in the subject, and body or it doesn’t send anything and instead you get an email telling you off for duplicate emails.

So with the copy re-sent, I could confirm no domain hopping, meaning no problems. So now I could reuse the email once more, add an apology at the top and resend.


Lessons from all this!

So what have I learnt? This was frustrating as I feel like I did my side of the testing and it was just unfortunate it went wrong but there are still a few good lessons for anyone to take away.

  1. In 2020 NOTHING should default over http, there just is not a valid reason to not provide a HTTPS endpoint. This is not Buttondown’s fault particularly but Mailgun’s and it’s inexcusable. With more and more sites using HSTS (including whole TLDs like .dev) and with Firefox having a HTTPS only mode. This is going to start being a real issue.
  2. If you are providing something as Privacy First I read that as privacy by default. Some of that is on me, the documentation does say you can turn off, rather than turn on. But the option is somewhat hidden and finding it was reminiscent of trying to find plans for Intergalactic Highways. I really don’t want to moan about Buttondown, that’s not the point of this article but if I was to moan, finding information is not easy, I mean the pricing page doesn’t even have, well, pricing! It is a 1-man project with all that comes with it. Anyway it was on me because I misread, but I feel also a little bit like it was cheeky sales material.
  3. I give talks on security headers, I manage a WordPress Security Headers plugin, I know HSTS headers can cause issues, but I will be honest this is the first time I have actually had this happen where it’s anything but a little annoying. If you are enabling HSTS header, you are enabling it for “life” and for everything on that domain. I still believe that’s a good thing, but it’s important to understand and account for.
  4. Apparently people don’t mind you screwing up, in fact it was a bit of a double whammy, because while I was tweeting apologies and fixing the issue, folks seeing those tweets were signing up to the email except…

    This was entirely my own fault, I managed to forget to include name="email" so it wasn’t passing the email field. DOH! Worse, it was working fine on the homepage, the homepage which should have been the same reusable Block, except I, for some reason, hard coded one but not the other!

Oh well, all in all far worse things have happened but it was a good learning exercise and, do you know what, I actually still really like Buttondown.

So will leave you with this final thought.

Helping you and your customers stay safe

WordPress Security Consulting Services

Power Hour Consulting

Want to get expert advice on your site's security? Whether you're dealing with a hacked site or looking to future-proof your security, Tim will provide personalised guidance and answer any questions you may have. A power hour call is an ideal starting place for a project or a way to break deadlocks in complex problems.

Learn more

Site Reviews

Want to feel confident about your site's security and performance? A website review from Tim has got you covered. Using a powerful combination of automated and manual testing to analyse your site for any potential vulnerabilities or performance issues. With a comprehensive report and, importantly, recommendations for each action required.

Learn more

Code Reviews

Is your plugin or theme code secure and performing at its best? Tim provides a comprehensive code review, that combine the power of manual and automated testing, as well as a line-by-line analysis of your code base. With actionable insights, to help you optimise your code's security and performance.

Learn more

Or let's chat about your security?

Book a FREE 20 minute call with me to see how you can improve your WordPress Security.

(No Strings Attached, honest!)