Pages

Could be the same reason you can't play the violin anymore.

Seriously, though, you haven't provided enough information for anyone out here to even attempt a guess.

What steps are you taking to attempt to email a Pages document?

What does your Mac do when you make that attempt?

Other useful information might include the version of OS X you are using (found in About this Mac, first item in the Apple menu)?

What version of Pages are you using (Found in the Application menu—named Pages when Pages is the active application)?

What email application are you using (and what version of that application)?

Are you able to email documents from other applications?

The more detail you provide, the more likely it is that someone here will be able to answer your question.

Regards,

Barry