Nope
@ptnijssen or @arjenbos (owner of the package on gridhub) have to look into this
I had a look at DPD a while back, but they dont have a json response only a html response. So you probably have to do a lot of filtering to get data out neatly.
See also support for letters? (not a issue, but a question). · Issue #8 · arjenbos/ha-postnl · GitHub
Letters is not available currently. Best to reply on github I suppose.