@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.