Re-using email rules with SimpleLogin alias

Not sure where to ask this, so here goes.

I use a variety of email rules to auto file my emails into certain folders in my email account (so I know what’s urgent and what’s not). These rules are based on the alias that is receiving the email.

I often need to add extra info to an email I have already received eg - add an invoice to correspondence about an order; add a licence file to a software purchase order; etc. This means I can keep all the associated information together.

I then re-send the mail to myself expecting it to be sent to the relevant folder in the email account. Of course this fails miserably - and I get various errors as I cannot send an email to my own alias.

Is there a clever way to make this work? I’m using iCloud mail which is fairly limited with server based email rules.