mail.app: sender's name but no address

[JBsea]

I received an email through Mac mail.app from a sender with no email address. The person's name was displayed (for example: John_Smith) but there is no email address. However, in the subject line it reads (for example) jsmith@website.com. It seems like a scam.... has anyone ever seen this before?

Thanks.

 

[MisterMe]

And if it is not a scam, what will you do?

 

[JBsea]

If I'm 100% positive it's not a scam, I would reply since it appears to be a recruiter and I'm looking for a job. It does not really matter though, I'm wondering how this happened: how can an email be sent with the email address not showing up in mail.app. Also, email address is not displayed in iOS Mail either.

Mac OSX 10.6.8
MacBook Pro
iPhone 4
iOS 6.1.3