Links in Email Signature does they somehow effect SEO of the site?
No they doesn't effect SEO at all.
Since your emails are not indexed by Google, no.
Of course, as a general business practice, what to include in your signature is up for discussion. It can certainly generate traffic. Google claims not to pay attention to Google Analytics data including traffic sources etc. so it is unlikely to have any benefit other than the direct traffic from the person visiting your site.
No it doesn't effect but why do you ask anyway?
Thanks for the info guys.