In February 2024 Google and Yahoo's email divisions implemented big changes to how emails could be delivered and if they would be deemed spam or junk mail.
The fact you're even reading this in your inbox, if that's even where you're reading it, is a miracle.
If you haven't updated your SPF, DKIM, and DMARC records this year, it's likely people aren't even getting your price guide when they enquire.
Eman's tips helped me fix my DNS settings.
How to fix this?
There's never been a better time to get your own domain name - like iamareallycoolcelebrant.com - if you don't already I recommend Aussie company, VentraIP, then to use a really good email host like Melbourne's Fastmail to host your actual email - follow all their instruction - and then if you do bulk emailing like I do: Buttondown, that link gets you a $9 discount.