Fix re-test in secure Icedove autoconfig wizard

research how to fix the "Re-test fails in the account creation wizard manual configuration window": Icedove ignores proxy settings, tries to connect to the Internet directly, and is forbidden to.

Parent Task: #6154 (closed)

Related issues

Related to #6369 (closed)

Original created by @tails on 6157 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information