Error in send mail task

I have a script task in which I check the size of a file.

If the size of a file is greater then 0 KB then I need to send this file as an attachment using send email task.

If size is equal to 0 KB then I don't want to send email at all.

In the script task, I have a flag(@.sFileExists) which i set to true in case of size of file greater then 0 and false in other case.

I am using a precedance constraint (Expression : @.sFileExists=true) and condition is logical AND.

After script task based on the condition (@.sFileExists=true) I am using the send email task for sending the email.

But I am not receiving the email. Please sugest where I am wrong.

Please note that the send email task is working all-right separately.

Do you get any error?
Does the task gets executed at all (when debugging in BIDS - does it turn green)?