Support for Email Sending via HTTP API (e.g., MailerSend) as SMTP Ports Are Commonly Blocked on VPS

Hi,

First of all, thanks a lot for maintaining Vaultwarden. I've been using it on a small VPS and it's been working great overall.

However, I ran into an issue that I think others might also face.
Most VPS providers (like mine) block outbound SMTP ports (25, 465, 587) by default, which makes it impossible to send emails through Vaultwarden's current SMTP setup.

This is a bit of a blocker, especially for things like password reset emails and email verification.

Would it be possible to add support for sending emails via HTTP APIs as an alternative?
For example, services like [MailerSend]( offer email sending via a simple API over HTTPS (port 443), which works fine even when SMTP is blocked.

I think this could help a lot of users who are hosting Vaultwarden on similar restricted servers.

Thanks again for your work!
Let me know if there's any workaround or if you'd consider this for a future update.