I cannot "Sign In" my Website, Failed to send Email!


I created my website with DigitalOcean OneClick Installation. After installation, I created first blog admin user and I posted some test blogs and pages. Everything was good. After some hours I wanted to add some new things but I could not Sign In. I am sure with my Pass and Mailadress etc. but it doesn’t work.

When I try to get new password with ‘Password Forget’ then I get this message: Failed to send email.

How I can fix the problem?