It is standard practice to remove these as well as any other signature parts like Thanks and the writers name.
There are many threads on http://meta.stackexchange.com setting out the reasons including this question as a FAQ
and according to that the following should be in our FAQ(however I can't find the FAQ)
Can I use a signature or tagline?
Please don't use signatures or taglines in your posts. Every post you make is already "signed" with your standard user card, which links directly back to your user page. Your user page belongs to you — fill it with interesting information about your interests, cool stuff you've worked on, or whatever else you like!
for email addresses alone see this question
...The goal of Stack Overflow is to create a resource of knowledge to help people for years to come, and this means the focus is squarely on questions and answers.
If I post a question and then ask people to email me the answers, this doesn't help future visitors. If I'm a spammer posting an email address so I can sell you my service, this creates a lot of noise that detracts from excellent Q&A. If I post my email address, at minimum, I'm opening the door for spammers to obtain my email address.