I use Thunderbird for many years and befor I used IE, I can not remember that I used Edge maybe to test it but that is all.
However I copy the link into a new tab just like Biggerdave wrote and put https in front of it but still did not work.
And it is stranges that I could download Great Brittan which also had http just like Netherlands and Singapor which I could not download.
This is a part of what I see when I click the download link :
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I try to download it again since you change http into https and it still did not work for the 2 countries.
But it works with the last link
noref.php?url=https://www.dosyaupload.com/2AG7/Postcodes.rarThank you for that