MyBB Community Forums

For my forum I've got a reply notification without any "from email".
I'm attaching the email + admin config clip.

I've exact same configuration setup but it's working fine.

What could be the reason?

have you checked full mail headers .. what does it say about from address. see also this (#16)

I've gone thru it but does not help. My first mybb forum is http://forum.indianworkingwoman.org . This same forum I've reused to create another forum : http://forum.indiaconsumercomplaints.org - surprisingly this "Unknown sender" problem is occuring in the first forum and not in the second.

I've compared the config and settings.php files in inc and setting are similar. I don't know what the problem is.

Also registration mail has no problem however new reply notification has this problem.