Same problem with bitbucket:
// dub.sdl
name "mailtest"
description "A minimal D application."
dependency "vibemail" version="~>2.0.3"
$ dub build
Fetching vibemail 2.0.3 (getting selected version)...
Failed to download package vibemail from https://dub-registry.herokuapp.com/packages/vibemail/2.0.3.zip