Need help with emails containing malware

As the title suggests I need some help with stopping some spam/potential malware. Yesterday I received a suspicious email. It was a "reply" to an email discussion from someone making very convincing argument to be someone I know. Essentially the name of the person, the subject line, and the body of the email were all from this previous discussion. The part that caught my attention was the attachment. I didn't expect an attachment for a reply on this particular conversation. And then I noticed that the attachment was a Zip file and the body of the email also contained a password. Immediate Red Flag! So I looked back at the email address next to the name and it was not the correct email address of the person. I flagged the email as spam but I was still very concerned as I felt this other person may have been hacked. A few hours later and I received a similar email, but from an entirely different discussion.

A few hours later I discovered that another party was involved in these email discussions. That person apparently opened an attachment on another email a few days earlier. So here is what I believe may have happened. When that attachment was opened it gave some hacker access to the email, username, and password of this person. The hacker has used this info to retrieve emails from this person's account. The hacker is using these emails to send malware to others that had recent discussions with this person.

So how do I stop the emails from coming in?

Unfortunately this is a business email address and others in our office are also getting emails, so I liked to try and stop them from getting in.
Email is an account with my ISP. We do not have our own email server. I contacted the ISP and was told they couldn't really do anything.
Of the 10 emails I have received with this style so far, only 2 have been flagged by AVG as containing a virus and been quarantined. Others have reported similar results.

Any help is greatly appreciated, I'm not even sure what to search the internet for, results have been unrelated.

Hello Mike.
We're here to help.
Email shield component in AVG Internet Security scans for threats in your incoming and outgoing email messages.
If any malicious activity is found, AVG will alert you immediately.
We appreciate your attention in determining the emails were spam.
Rest assured, AVG will automatically scan your incoming and outgoing emails.

But AVG only flagged 2 of the emails as malware? So it's not finding everything.

But AVG only flagged 2 of the emails as malware? So it's not finding everything.

Hello Mike.
We're here to help.
Email shield component in AVG Internet Security scans for threats in your incoming and outgoing email messages.
If any malicious activity is found, AVG will alert you immediately.
We appreciate your attention in determining the emails were spam.
Rest assured, AVG will automatically scan your incoming and outgoing emails.

We understand your concern.

As mentioned earlier, AVG will scan for threats in your incoming and outgoing email messages. However, it wont block the spam email.

AVG will detect the malicious content in the email attachment.

Did you have an attachment in all the 10 email?

Keep us posted.