@crossingthethreshold so yeah I did move over to Mailer Lite. It’s been 95% there. I raised a support ticket which was acknowledged but never resolved. Then there was the issue that their website isn’t 100% on the iPad and so there are some issues. Button down is best for very simple text based email only. You can control some elements like bold, italics, and headings - apart from that I would really lower my expectations :). I think that if you are only really interested in sending out text, it’s a great option. What’s the problems you are running against?

@kaa Thank you for this. I have set up a custom domain and (I believe) setup the required DNS settings. Sometimes Buttondown is showing that the settings are correct and other times that they are not. In both cases my email/newsletter won't send. When Buttondown tells me that they are incorrect, the settings that it asks me to enter appear to be what I have already set. I have been in touch with support and after initial replies, all has gone quiet now. I could remove the custom domain, but I am still aware of something not quite right. I am no expert on DNS settings, but I'm pretty sure that I have followed the instructions correctly.