Although, the emails said they were from "DPD delivery," they wee actually sent from another email address. This type of trickery is called email spoofing. It is used by cybercriminals to trick potential victims into believing an email came from a legitimate source, when it was actually sent by them.
How to Determine if an Email is a Scam
Hover your cursor over the link in the email to view the URL before you click it. If you don’t recognise the URL, website address, or destination, don’t open it. Go directly to DPD's website at www.dpd.co.uk and enter the tracking number yourself.