Fix From/Reply-To headers (T622657)

Summary:

• Fixes duplicate/wrong Reply-To and From header
• Don't use Laravel global settings, they don't play well with our tenants.
• We anyway can't check for Laravel global headers in our tests

Test Plan: ./phpunit

Reviewers: #hkccp_developers, mollekopf

Reviewed By: #hkccp_developers, mollekopf

Subscribers: mollekopf, #hkccp_developers

Differential Revision: https://git.kolab.org/D4382