From time to time I come across postings containing e-mail addresses. Should we remove those from the postings to help the users not getting spammed (of course also leaving a comment)?
If the user is asking for answer via email, like this:
Please send answers to
email@example.com(I can't be bothered to check the site)
Then yes, remove it. Leave a comment to make the user aware of this feature:
If the user posts their email address for another (valid) reason, use your best judgement. In general, it makes sense to remove the email address and leave a comment.
Try to estimate if the user knows what they're doing.
If someone posts another user's email address, remove it immediately, unless you have very good reason to believe the other person is okay with it.
Also remember that revisions can always be undone.
If you're really not sure, shoot first and ask questions later :)
MSO user 134432 has a nice summary on why this is a bad idea:
It's never safe to publish your email address on an open web site. If you want someone to get in touch set up a new temporary address and use that until you're sure you can trust them. Even if the people on the site are trustworthy there are people out there harvesting every publicly available email address and selling them to the spammers and mass marketers.
As a pro-forma comment, this could work:
(Welcome to Ask Ubuntu!) It's never safe to publish your email address on an open web site. I've removed it from the post. If you're sure you want it to be publicly visible, you can undo this revision.
If you realize you've posted an email address or other confidential information, edit your post to remove it. Past revisions are still publicly visible, but they are not indexed by Google. You can flag the post to request that the revision be deleted; moderators can't do that, but they can relay the request to a developer who can. Since this requires a lot of busy people to get involved, it's only to be done as a last resort; double-check before posting, especially when dealing with sensitive data such as logs.
Remember that even if the data is eventually deleted from the site, someone may have seen it and copied it. If you accidentally posted a password, consider it compromised and change it immediately.
If you see an email address or other confidential information in someone else's post, and you're pretty sure that this was done by mistake, edit the post to at least stop the information from being indexed by Google. Leave a note for the poster that he may want to escalate the removal further.