Script inside an email can be at the very least suspicious and Script-inf, usually indicates injected script code and that is most frequently found in web sites not so much emails.
I don’t use MS Outlook, so I can’t speak from personal experience.
Emails in Outlook aren’t in individual files, they are in folders now these folders are usually contained in an archive file in Outlook I think these are .pst files. I don’t know where you have been looking, but your image is indicating this was sent to the avast chest.
The issue is it keeps being re-infected. Not sure if this indicates the virus is trying to spread itself via email and avast is stopping that.
Or i’ve received an email with this attached & for some reason outlook has no record of the email & it keeps coming back.
Given something keeps getting continually detected in what is meant to be Incoming email, with what I would consider highly suspect subject and probably a social engineering/phishing attempt. Unless of course this an expected Tax Invoice, which I doubt.
There is a possibility that someone that you know is infected and his email address book has been harvested for spam/phishing purposes.
I don’t think that avast would just remove the attachment, but the whole email.
As I said I don’t use Outlook - so I wouldn’t know where to start digging to see this email still remains inside Outlooks folders/.pst files (if indeed they are still using .pst files to store multiple emails).
When does this alert happen, what were you doing, etc. ?
Have you been able to capture the avast alert screen ?