When sharing a topic by email with ipb 4.x, it create a page that is visible by search engines,

It is damageable because:  

• It doesn't bring added value to user and should not be present in SE indexes
• SE loose precious crawl time, crawling useless page.

So we have two things to correct:  

• The page ( /?do=email ) should have cannonical and nofollow meta header
• The link should have rel=nofollow

I don't think it's something big

UP ?

We added...

Disallow: /*do=email

to robots.txt.

Same problem here. It seems that the issue will be solved on 4.1.16.