Any error message would be helpful.
But if you see something like this in the return message: "message rejected AUP#SNDR", than you need to talk to your email provider and request to have a DKIM record set.

What Is a DKIM Record? Everything You Need To Know and More (hostinger.com)

Cheers,
-- Bernd

Hello, I have a problem sending mail. I receive a lot of emails and I try to reply to them, but unfortunately I get a message that the message failed to send. Can I know the solution and why?
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