Summary: deploy a new sender-rewriting mail forwarder, migrate mailing lists off the legacy server to a new machine, migrate the remaining Schleuder list to the Tails server, upgrade eugeni.

• Background
• Proposal
  • Actual changes
    • Mailman 3 upgrade
    • New sender-rewriting mail exchanger
    • Schleuder migration
    • Upgrade legacy mail server
  • Goals
    • Must have
    • Nice to have
    • Non-Goals
  • Scope
  • Affected users
    • Personas
  • Timeline
    • Optimistic timeline
    • Worst case scenario
• Alternatives considered
• References
  • History
  • Personas descriptions
    • Ariel, the fundraiser
    • Blipblop, the bot
    • Gary, the support guy
    • John, the contractor
    • Mallory, the director
    • Nancy, the fancy sysadmin
    • Orpheus, the developer

Background

In #41773, we had yet another report of issues with mail delivery, particularly with email forwards, that are plaguing Gmail-backed aliases like grants@ and travel@.

This is becoming critical. It has been impeding people's capacity of using their email at work for a while, but it's been more acute since google's recent changes in email validation (see #41399) as now hosts that have adopted the SPF/DKIM rules are bouncing.

On top of that, we're way behind on our buster upgrade schedule. We still have to upgrade our primary mail server, eugeni. The plan for that (TPA-RFC-45, #41009) was to basically re-architecture everything. That won't happen fast enough for the LTS retirement which we have crossed two months ago (in July 2024) already.

So, in essence, our main mail server is unsupported now, and we need to fix this as soon as possible

Finally, we also have problems with certain servers (e.g. state.gov) that seem to dislike our bespoke certificate authority (CA) which makes receiving mails difficult for us.

Proposal

So those are the main problems to fix:

• Email forwarding is broken
• Email reception is unreliable over TLS for some servers
• Mail server is out of date and hard to upgrade (mostly because of Mailman)

Actual changes

The proposed solution is:

• Mailman 3 upgrade (#40471)

• New sender-rewriting mail exchanger (#40987)

• Schleuder migration

• Upgrade legacy mail server (#40694)

Mailman 3 upgrade

Build a new mailing list server to host the upgraded Mailman 3 service. Move old lists over and convert them while retaining the old archives available for posterity.

This includes lots of URL changes and user-visible disruption, little can be done to work around that necessary change. We'll do our best to come up with redirections and rewrite rules, but ultimately this is a disruptive change.

This involves yet another authentication system being rolled out, as Mailman 3 has its own user database, just like Mailman 2. At least it's one user per site, instead of per list, so it's a slight improvement.

This is issue #40471.

New sender-rewriting mail exchanger

This step is carried over from TPA-RFC-45, mostly unchanged.

Configure a new "mail exchanger" (MX) server with TLS certificates signed by our normal public CA (Let's Encrypt). This replaces that part of eugeni, will hopefully resolve issues with state.gov and others (#41073, #41287, #40202, #33413).

This would handle forwarding mail to other services (e.g. mailing lists) but also end-users.

To work around reputation problems with forwards (#40632, #41524, #41773), deploy a Sender Rewriting Scheme (SRS) with postsrsd (packaged in Debian, but not in the best shape) and postforward (not packaged in Debian, but zero-dependency Golang program).

It's possible deploying ARC headers with OpenARC, Fastmail's authentication milter (which apparently works better), or rspamd's arc module might be sufficient as well, to be tested.

Having it on a separate mail exchanger will make it easier to swap in and out of the infrastructure if problems would occur.

The mail exchangers should also sign outgoing mail with DKIM, and may start doing better validation of incoming mail.

Schleuder migration

Migrate the remaining mailing list left (the Community Council) to the Tails Shleuder server, retiring our Schleuder server entirely.

This requires configuring the Tails server to accept mail for @torproject.org.

Note that this may require changing the addresses of the existing Tails list to @torproject.org if Schleuder doesn't support virtual hosting (which is likely).

Upgrade legacy mail server

Once Mailman has been safely moved aside and is shown to be working correctly, upgrade Eugeni using the normal procedures. This should be a less disruptive upgrade, but is still risky because it's such an old box with lots of legacy.

One key idea of this proposal is to keep the legacy mail server, eugeni, in place. It will continue handling the "MTA" (Mail Transfer Agent) work, which is to relay mail for other hosts, as a legacy system.

The full eugeni replacement is seen as too complicated and unnecessary at this stage. The legacy server will be isolated from the rewriting forwarder so that outgoing mail is mostly unaffected by the forwarding changes.

Goals

This is not an exhaustive solution to all our email problems, TPA-RFC-45 is that longer-term project.

Must have

• Up to date, supported infrastructure.

• Functional legacy email forwarding.

Nice to have

• Improve email forward deliverability to Gmail.

Non-Goals

• Clean email forwarding: email forwards may be mangled and rewritten to appear as coming from @torproject.org instead of the original address. This will be figured out at the implementation stage.

• Mailbox storage: out of scope, see TPA-RFC-45. It is hoped, however, that we eventually are able to provide such a service, as the sender-rewriting stuff might be too disruptive in the long run.

• Technical debt: we keep the legacy mail server, eugeni.

• Improved monitoring: we won't have a better view in how well we can deliver email.

• High availability: the new servers will not add additional "single point of failures", but will not improve our availability situation (issue #40604)

Scope

This proposal affects the all inbound and outbound email services hosted under torproject.org. Services hosted under torproject.net are not affected.

It also does not address directly phishing and scamming attacks (#40596), but it is hoped the new mail exchanger will provide a place where it is easier to make such improvements in the future.

Affected users

This affects all users which interact with torproject.org and its subdomains over email. It particularly affects all "tor-internal" users, users with LDAP accounts, or forwards under @torproject.org, as their mails will get rewritten on the way out.

Personas

Here we collect a few "personas" and try to see how the changes will affect them, largely derived from TPA-RFC-45, but without the alpha/beta/prod test groups.

For all users, a common impact is that emails will be rewritten by the sender rewriting system. As mentioned above, the impact of this still remains to be clarified, but at least the hidden Return-Path header will be changed for bounces to go to our servers.

Actual personas are in the Reference section, see Personas descriptions.

Timeline

Optimistic timeline

• Late September (W39): issue raised again, proposal drafted (now)
• October:
  • W40: proposal approved, installing new rewriting server
  • W41: rewriting server deployment, new mailman 3 server
  • W42: mailman 3 mailing list conversion tests, users required for testing
  • W43: mailman 2 retirement, mailman 3 in production
  • W44: Schleuder mailing list migration
• November:
  • W45: eugeni upgrade

Worst case scenario

• Late September (W39): issue raised again, proposal drafted (now)
• October:
  • W40: proposal approved, installing new rewriting server
  • W41-44: difficult rewriting server deployment
• November:
  • W44-W48: difficult mailman 3 mailing list conversion and testing
• December:
  • W49: Schleuder mailing list migration vetoed, Schleuder stays on eugeni
  • W50-W51: eugeni upgrade postponed to 2025
• January 2025:
  • W3: eugeni upgrade

Alternatives considered

We decided to not just run the sender-rewriting on the legacy mail server because too many things are tangled up in that server. It is just too risky.

We have also decided to not upgrade Mailman in place for the same reason: it's seen as too risky as well, because we'd first need to upgrade the Debian base system and if that fails, rolling back is too hard.

References

• discussion issue

History

This is the the fifth proposal about our email services, here are the previous ones:

• TPA-RFC-15: Email services (rejected, replaced with TPA-RFC-31)
• TPA-RFC-31: outsource email services (rejected, in favor of TPA-RFC-44 and following)
• TPA-RFC-44: Email emergency recovery, phase A (standard, and mostly implemented except the sender-rewriting)
• TPA-RFC-45: Mail architecture (still draft)

Personas descriptions

Ariel, the fundraiser

Ariel does a lot of mailing. From talking to fundraisers through their normal inbox to doing mass newsletters to thousands of people on CiviCRM, they get a lot done and make sure we have bread on the table at the end of the month. They're awesome and we want to make them happy.

Email is absolutely mission critical for them. Sometimes email gets lost and that's a major problem. They frequently tell partners their personal Gmail account address to work around those problems. Sometimes they send individual emails through CiviCRM because it doesn't work through Gmail!

Their email forwards to Google Mail and they now have an LDAP account to do email delivery.

Blipblop, the bot

Blipblop is not a real human being, it's a program that receives mails and acts on them. It can send you a list of bridges (bridgedb), or a copy of the Tor program (gettor), when requested. It has a brother bot called Nagios/Icinga who also sends unsolicited mail when things fail.

There are also bots that sends email when commits get pushed to some secret git repositories.

Gary, the support guy

Gary is the ticket overlord. He eats tickets for breakfast, then files 10 more before coffee. A hundred tickets is just a normal day at the office. Tickets come in through email, RT, Discourse, Telegram, Snapchat and soon, TikTok dances.

Email is absolutely mission critical, but some days he wishes there could be slightly less of it. He deals with a lot of spam, and surely something could be done about that.

His mail forwards to Riseup and he reads his mail over Thunderbird and sometimes webmail. Some time after TPA-RFC_44, Gary managed to finally get an OpenPGP key setup and TPA made him a LDAP account so he can use the submission server. He has already abandoned the Riseup webmail for TPO-related email, since it cannot relay mail through the submission server.

John, the contractor

John is a freelance contractor that's really into privacy. He runs his own relays with some cools hacks on Amazon, automatically deployed with Terraform. He typically run his own infra in the cloud, but for email he just got tired of fighting and moved his stuff to Microsoft's Office 365 and Outlook.

Email is important, but not absolutely mission critical. The submission server doesn't currently work because Outlook doesn't allow you to add just an SMTP server. John does have an LDAP account, however.

Mallory, the director

Mallory also does a lot of mailing. She's on about a dozen aliases and mailing lists from accounting to HR and other unfathomable things. She also deals with funders, job applicants, contractors, volunteers, and staff.

Email is absolutely mission critical for her. She often fails to contact funders and critical partners because state.gov blocks our email -- or we block theirs! Sometimes, she gets told through LinkedIn that a job application failed, because mail bounced at Gmail.

She has an LDAP account and it forwards to Gmail. She uses Apple Mail to read their mail.

Nancy, the fancy sysadmin

Nancy has all the elite skills in the world. She can configure a Postfix server with her left hand while her right hand writes the Puppet manifest for the Dovecot authentication backend. She browses her mail through a UUCP over SSH tunnel using mutt. She runs her own mail server in her basement since 1996.

Email is a pain in the back and she kind of hates it, but she still believes entitled to run their own mail server.

Her email is, of course, hosted on her own mail server, and she has an LDAP account. She has already reconfigured her Postfix server to relay mail through the submission servers.

Orpheus, the developer

Orpheus doesn't particular like or dislike email, but sometimes has to use it to talk to people instead of compilers. They sometimes have to talk to funders (#grantlyfe), external researchers, teammates or other teams, and that often happens over email. Sometimes email is used to get important things like ticket updates from GitLab or security disclosures from third parties.

They have an LDAP account and it forwards to their self-hosted mail server on a OVH virtual machine. They have already reconfigured their mail server to relay mail over SSH through the jump host, to the surprise of the TPA team.

Email is not mission critical, and it's kind of nice when it goes down because they can get in the zone, but it should really be working eventually.