URGENT: Is sendmail working for other users?

URGENT: Is sendmail working for other users?

sendmail stopped working this morning in our production code.

I wrote this simple test function just to see if emails are being sent. They are NOT. I checked my account usage, I'm not over my email quota. 

void WalkIn.OM.Temp.Test()
{
    sendmail
    (
        To       :  " lex.shan@walkintour.com"
        From     :  zoho.loginuserid 
        Subject  :  "zoho testing email subject" 
        Message  :  "zoho testing email body"
    )
}