Emails are very easily forged. The only thing really telling you who sent an email is the 'From:' header, which is ridiculously easily forged. Any email server in the world can at any time send emails 'From:
president@whitehouse.gov' and it will get sent just fine. There's some sanity checks email servers can do to look for very blatant forgeries, but it varies wildly in sophistication and accuracy between email services.
A common scam is to use a forged 'From:
trustworthy@company.biz' and supply a real 'Reply-To:
pajeet@indiamail.com' which causes your reply to automatically address the Reply-To instead of the From address. If someone is just trying to cause problems, they might not supply a Reply-To but might supply a real From hoping you don't respond to it and just react on it.