Rapidcart and digital files issue

Has anyone ever had the following issue, as I’m looking for advice from anyone who may have experienced this.
I’m selling digital downloads of pdf files. Using rapidcart pro and amazon web services. Most of the time the online shop works correctly. I have made numerous test purchases all of which have worked but I am experiencing a problem when buyers (particularly from outside the UK) purchase downloads using a hotmail address . PayPal is processing the payment and sending me the copy of the confirmation email but the customer is not receiving their download link. I have asked customers to check junk mail but they have found nothing there either, It seems to happen randomly but nearly all the errors have occurred when people have hotmail .GMX or .fr email addresses.
Anyone experienced this?

I’m in the US and most sales of our eBooks and video downloads are in this country. Regardless of whether the download is a zip file or native pdf, ePub, mobi, etc customers often fail to get their download email. I’ve seen this for years now. I’ve come to accept it and simply attribute it to filters and lists trashing the emails before it even gets to the customers email server. On our product pages we tell customers to add the proper email address to their contact list, approved senders, etc etc etc but that has all been no help. I simply accept it now with a smile happy to have had a sale. Good luck.

Oh, btw, it also doesn’t matter if the email is coming from our 3rd party cart or another source. Sometimes when I send a download link myself it takes 3-4 tries.

What system is sending the digital attachment email or is it a link to download the digital attachment in an email?

rapid cart sends a link to download the product from a download page on the site via an auto generated email. I quite often get the email from papa to say the sale has gone through but then the customer isn’t getting the email from the website with the download link in it.