Local Tory parties are sending out letters asking people to sign up for postal votes, with an application form for a postal vote (genuine).
They are providing a free post envelope to send it back in.
This free post envelope does not go to the electoral services office address on the form, it goes to the local Tory party office.
They can then look at the form, see your details and know that you're wanting a postal vote (so can target you earlier in the election campaign). They will also know that you read mail from the conservatives.
Hopefully they will then pass your postal vote application form onto the correct address, but who knows?
Here's an example from twitter. People in a different area have also received one, but the free post envelope did not mention the Conservatives, it's only googling that showed the real destination.
twitter.com/markdpryan/status/1637165173734612999?s=61&t=U9XrcF693-JpMxeIueYG7g