Receiving Null error while sending an e-mail in Zoho

Receiving Null error while sending an e-mail in Zoho

Hi , 

I'm trying to send an e-mail from Zoho with my G-mail address. 
Everything in the parameters is correct; my g-mail is added and the e-mails I send from G-mail are linked to the client in Zoho. 
But when I'm trying to send an e-mail from Zoho itself; I get the "Null" error. 

My pasword for G-mail has been changed; I think that's the problem but I don't see where to update 
it !
 

Thanks in advance!