Unable to send emails

[mulligan]

I cannot Forward, Reply or Send new message.  There is a red triangle and in red - An error occurred.  Underneath that - SMTP Error (-1): Connection to server failed.
Please help.  Thank you.
Suzanne

[JohnDoh]

Please contact your email provider for support. Roundcube is the name of the webmail software they are using, it is not a service.