I'm in the process of developing a product which will send emails. For context, it is for hospitals that want to email patients for a number of reasons. i.e. it's not a spam system. It's a Windows product and I'm on a budget and I don't have access to an MS Exchange server to test and looking into it, Exchange is complex to set (it needs a domain server, and I don't have the skills/resources to set these up).
I previously used a couple of yahoo accounts for testing, but although I can still send email from them manually, they don't receive any emails I send to them programmatically (through their own accounts). It's not been very high volume, but I was sending one email a minute for about an hour at one point, occasionally 5 at once. The emails aren't in the spam folders, they just disappear with no errors raised in my client as though yahoo receives them and throws them away. For info, I've ensured that "2-step verification" = OFF and "allow apps that use less secure sign in" = ON.
Is there a way I can get these accounts going again? Alternatively, could someone point me to a cheap (preferably free) and easy method to have access to a SMTP/POP server where I can send emails to a small number of demo accounts, occasionally several a minute, without the thought police setting in? I'm sending from .Net using the libraries in System.Net.Mail.
Any advice gratefully received.