activate email sent to client

Hi,

I have a scenario for a package with 1 document and 2 signers, only 1 signer required to sign the document.

when this package sent , both of the signers received the activate email (1 signer for signing, and another signer just review - no  signature required. 

then I change the package to DRAFT and Re-send, at this moment, only 1 signer which need to sign receive the activate email, but not the 2nd signer doesn't receive the email. 

From the package perspective, it hasn't been changed anything. why 1st time and 2nd time to 'SEND" package has different email behavior, is it expected?

thanks,

Cindy