Email Error: The following From address failed:

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Hi, I am having problems with Zen Cart email options. I keep getting the error:

Email Error: The following From address failed: example######################.au

I tried doing many things but failed to succeed. my settings for the Email Options are below:

E-Mail Transport Method smtp
E-Mail Linefeeds LF   
Use MIME HTML When Sending Emails false   
Send E-Mails true   
Verify E-Mail Addresses Through DNS false   
Email Archiving Active? true   
E-Mail Friendly-Errors false   
Email Address (Displayed to Contact you) example######################.au
Email Address (sent FROM) example######################.au
Emails must send from known domain? No   
Email Admin Format? TEXT   
Send Copy of Order Confirmation Emails To example######################.au   
Send Copy of Create Account Emails To - Status 0   
Send Copy of Create Account Emails To example######################.au  
Send Copy of Tell a Friend Emails To - Status 0   
Send Copy of Tell a Friend Emails To example######################.au 
Send Copy of Customer GV Send Emails To - Status 0   
Send Copy of Customer GV Send Emails To example######################.au
Send Copy of Admin GV Mail Emails To - Status 0   
Send Copy of Customer Admin GV Mail Emails To example######################.au 
Send Copy of Admin Discount Coupon Mail Emails To - Status 0   
Send Copy of Customer Admin Discount Coupon Mail Emails To example######################.au   
Send Copy of Admin Orders Status Emails To - Status 0   
Send Copy of Admin Orders Status Emails To example######################.au
Send Notice of Pending Reviews Emails To - Status 0   
Send Notice of Pending Reviews Emails To example######################.au
Set "Contact Us" Email Dropdown List    
Allow Guest To Tell A Friend true   
Contact Us - Show Store Name and Address 1   
Send Low Stock Emails 0   
Send Low Stock Emails To example######################.au
Display "Newsletter Unsubscribe" Link? true   
Audience-Select Count Display true   
SMTP Email Account Mailbox example
SMTP Email Account Password examplepassword
SMTP Email Mail Host smtp.mail.yahoo.com.au   
SMTP Email Mail Server Port 587   
Convert currencies for Text emails £,£:€,€

Please help as this has been fustrating me for the past 2 weeks!!

Thanking everyone in advanced.

Kind Regards,

me