Email notifications show broken images (due to authenticated media)

[turt2live]

Description

Reported on behalf of a conversation I saw: Email notifications use the legacy, unauthenticated, and deprecated URLs for avatars of rooms/senders, which don't work when authenticated media is in full force. This leads to the "broken image" placeholder in browsers/email clients.

The easiest fix is to remove the img elements entirely, as it's questionable to include them from a Trust & Safety perspective anyways (at least until there's better tooling available). Magic URLs like how bridges work may be desirable in the long term.

Steps to reproduce

• receive an email notification

Homeserver

matrix.org

Synapse Version

whatever matrix.org runs

Installation Method

Other (please mention below)

Database

postgresql

Workers

Single process

Platform

matrix.org

Configuration

No response

Relevant log output

see matrix.org

Anything else that would be useful to know?

No response