[Enhancement] Display inbound rejections to the user.

[RokeJulianLockhart]

Prerequisites

1. I have searched open and closed issues for duplicates

2. This isn't a feature request

3. This is not a report about my app not working as expected

Problem And Solution

The rationale is explained in the context of anonaddy/anonaddy#672 (comment).

Tasks

1. File this as a suggestion at protonmail.uservoice.com/#suggestion_title.