If your email ID is different from your own name, it will be a good idea to have a signature entry with your name and position in the company. You should own up responsibility for what you are writing. Do not write anything you would not say in public. There is nothing like total privacy in email communication.
This is where you need to use a disclaimer with every message. [Email disclaimers are statements that are either prepended or appended to e-mails.] If someone in your company sends messages that are racist or otherwise offensive, the company has to answer for it. The disclaimer can reduce the company’s risk, if it includes a statement that the employees of the company have been instructed not to send offensive material in their messages.
Your company should frame an email policy and train the employees to abide by the guidelines laid down. By doing this, who knows, you may be avoiding costly defamation suits. Link.