<human>: Back in early February I quit my old job and started a new one in a completely different field. (Old - retail, new - tv installation technician)

Today I received a call from my boss accusing me of sending an email to everyone in the company in reponse to an angry email a different employee sent after he was fired.

Apparently he thought it would be a good idea to send off an email to everybody in the company to let them all know what he thought was wrong with it in what has been described as a vulgar manner.

Then sombody sent off a response email from my old stores email address saying "this guy has a pont[sic]"

My old boss couldn't get anyone to fess up to sending it so she had the computer tech for the company trace where the email was sent from, according to my boss it was sent from my IP and postal code.

The first I heard of this stupid fiasco was today when my boss called to accuse me. And according to her nobody else lives near me or would share the same postal code.

Is it possible for someone to fake my ip address and log into my old works email? 

Could they do this remotely?

Should I be worried about anything like a keylogger on my computer?

Is she just pulling this out of her ass because she doesn't have any other leads?

I was working out of city the day it occured and I don't have any friends in the old job so nobody would have come to my house and done it on my computer.

Summarize the given text in a few sentences.
<bot>: Old boss accused me of supporting another ex-employee badmouthing the company via email. Says she has proof that the email came from my ip address / postal code.