**Warning**: This release removes the example email notification templates from
`res/templates` (they are now internal to the python package). This should only
affect you if you (a) deploy your Synapse instance from a git checkout or a
github snapshot URL, and (b) have email notifications enabled.

If you have email notifications enabled, you should ensure that
`email.template_dir` is either configured to point at a directory where you
have installed customised templates, or leave it unset to use the default

The configuration parser will try to detect the situation where
`email.template_dir` is incorrectly set to `res/templates` and do the right
thing, but will warn about this.


- Ship the example email templates as part of the package ([\#4052](https://github.com/matrix-org/synapse/issues/4052))
- Add support for end-to-end key backup (MSC1687) ([\#4019](https://github.com/matrix-org/synapse/issues/4019))


- Fix bug which made get_missing_events return too few events ([\#4045](https://github.com/matrix-org/synapse/issues/4045))
- Fix bug in event persistence logic which caused 'NoneType is not iterable' ([\#3995](https://github.com/matrix-org/synapse/issues/3995))
- Fix exception in background metrics collection ([\#3996](https://github.com/matrix-org/synapse/issues/3996))
- Fix exception handling in fetching remote profiles ([\#3997](https://github.com/matrix-org/synapse/issues/3997))
- Fix handling of rejected threepid invites ([\#3999](https://github.com/matrix-org/synapse/issues/3999))
- Workers now start on Python 3. ([\#4027](https://github.com/matrix-org/synapse/issues/4027))
- Synapse now starts on Python 3.7. ([\#4033](https://github.com/matrix-org/synapse/issues/4033))

Internal Changes

- Log exceptions in looping calls ([\#4008](https://github.com/matrix-org/synapse/issues/4008))
- Optimisation for serving federation requests ([\#4017](https://github.com/matrix-org/synapse/issues/4017))
- Add metric to count number of non-empty sync responses ([\#4022](https://github.com/matrix-org/synapse/issues/4022))
This tag has no release notes.