Impossible to send email : SMTP error

Impossible to send email : SMTP error

Hello Zoho Team,

Since some days, I've this message after trying sending emails :
Unable to connect SMTP server:auth.smtp.1and1.fr Reason:Unknown host:

and when I'm trying to fetch, I've this message :
Problem in connecting to the mail server

and after changing my password on server I've this message when I want to update my POP account :
Account is not valid

But when I'm using Mail program from my Macbook, it works fine.

Can you check what is going wrong on the web interface ?

Thanks

Daniel