At the moment, it is standard for a homeserver to require an identity server to be passed as part of adding an email to your HS account.

This will be changing for future Synapse versions as they learn to manage email themselves, but for the moment it is still the current state.

Riot Web on develop at the moment assumes we've already made it to ideal world, creating the following problem:

1. Disconnect from your IS in Settings
2. Try to add an email to your HS account
3. HS returns 400 error demanding an IS be passed

This can be reproduced on the termstest environment.