It's that time again: there's a new Synapse release, fresh out of the oven! Let's take a look at what's inside Synapse 1.64.

Delegating email verification is now deprecated

Synapse 1.4.0 introduced a configuration option ( to allow homeservers to delegate validating the ownership of email addresses to an external identity server. This validation is used by Synapse when adding an email address to a Matrix account, or before performing a password reset.

As of Synapse 1.64, this option is deprecated, and Synapse will print a warning if it is used. This is because this option relies on old API endpoints that have since been removed from the Matrix specification.

Synapse can do this validation internally provided it is configured with details of an SMTP server. Administrators currently relying on should therefore ensure that an SMTP server is correctly configured, and remove the option. See the configuration guide for more information.

We plan to fully remove this configuration option in Synapse 1.66, which is expected to be released on August 30th.

Note that the equivalent option to validate the ownership of phone numbers (account_threepid_delegates.msisdn) can still be used, though we expect to deprecate it in a future release of Synapse.

Improved TLS support for sending emails

When configuring an SMTP server to use to send out emails to users, server administrators can configure Synapse to use TLS to communicate to that server. Until now, only STARTTLS was supported in this case.

Synapse 1.64 introduces a new force_tls configuration option in the email section of the configuration file. If this new setting is set to true Synapse will use TLS for the initial connection rather than upgrading via STARTTLS.

See the configuration guide for more information.

Memory leak in frozendict

A couple of weeks ago, we identified a memory leak within frozendict, which is a library that Synapse relies on. This would in turn cause Synapse instances to slowly leak memory when processing /sync requests.

We highly encourage server administrators who installed Synapse via pip to upgrade their local version of frozendict to version 2.3.3 or later, which includes a fix to this issue. The Docker image matrixdotorg/synapse and the Debian packages from already include the updated library.

Everything else

This version of Synapse introduces support for room version 10! This new room version enables support for the new knock_restricted join rule, to allow knocking into rooms which are otherwise restricted to members of a specific room (or space). See the Matrix specification about room version 10 for more information.

Additionally, Synapse 1.64 features a new rate limiter to limit the rate of joins to the same room. It is intended as a mitigation against abuse scenarios involving joining a lot of users from different homeservers to a room to then send spam across it. See the configuration guide for more information.

This release of Synapse also extends the List Rooms and Room Details admin APIs to include the type of a room in responses, allowing server administrators to differentiate spaces from other rooms.

See the full changelog for a complete list of changes in this release. Also please have a look at the upgrade notes for this version.

Synapse is a Free and Open Source Software project, and we'd like to extend our thanks to everyone who contributed to this release, including (in no particular order) Beeper, andrewdoh, Thomas Weston, jejo86, villepeh, Jörg Behrmann and Jacek Kuśnierz, as well as anyone helping us make Synapse better by sharing their feedback and reporting issues.

The Foundation needs you

The Foundation is a non-profit and only relies on donations to operate. Its core mission is to maintain the Matrix Specification, but it does much more than that.

It maintains the homeserver and hosts several bridges for free. It fights for our collective rights to digital privacy and dignity.

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