TLS 1.0/1.1 deprecated in 03/2021. Wouldja disable them on SMTP/MTA by 08/2026 and not lose emails?

manish · July 24

TLS 1.0 and 1.1 were officially declared deprecated by the IETF in March 2021.

Google's Gmail still supports TLS 1.0, 1.1 and 3DES (outbound only) for compatibility with legacy systems.

If you ask a lot of seasoned admins, TLS 1.0 looks dead for email, TLS 1.1 is mostly used by scanners and spammers, with some real traffic, but rare. How does everyone feel about removing receive/send support for everything lower than TLS 1.2 currently.

I understand we have enough room to do best TLS magic with IMAPS/submissions or webmail, but when it comes to SMTP/MTA, there is always this feeling to continue to allow TLS 1.0/1.1 for now until the big ESPs start dropping support.

Dear Email Hosting providers:

How many emails have you received/sent with TLS 1.0/1.1 on SMTP/MTA over the period of past 12 months? This will help assess the risk of disabling TLS 1.0/1.1 by August 2026.

What are your thoughts?

Thank you!

Levi · July 24

Anything bellow 1.2 is a lazzy ass admin job. Deny it.

manish · July 24

@Levi said: Anything bellow 1.2 is a lazzy

is cool in theory, in practice may lose emails? Don't you think so? I have confirmation from admins who are still receiving emails with TLS 1.1.

yoursunny · July 24

Mentally strong people use PQC only.

manish · July 24

@yoursunny said: PQC only.

A+ TLS security is good, until you realize how email works! We should unquestionably set up the best TLS ciphers and protocols for IMAPS and submissions. Also, focus on better authentication methods, including client certificate (mTLS) authentication.

Levi · July 24

@manish said:

@Levi said: Anything bellow 1.2 is a lazzy

is cool in theory, in practice may lose emails? Don't you think so? I have confirmation from admins who are still receiving emails with TLS 1.1.

REJECT with clear error message served is enough. Why support legacy? All big email providers use TLS 1.3. Everything else is irrelevant if not up to standard.

nikio · July 24

It depends who sends you emails. If most of your emails come from the big ESPs, that's fine. If you are dealing with normies in Australia who still use telco emails (can Bigpond please just rm -rf/ itself already), then you're better off supporting SSLv2.

manish · July 24

@Levi said: All big email providers use TLS 1.3.

Bold statement. Much required.

Interestingly one of the biggest email provider Gmail is still lingering on to TLS 1.0 and even 3DES. Same with others including Zoho etc.

manish · July 24

@nikio said: better off supporting SSLv2.

Was Microsoft forced to write this? https://learn.microsoft.com/en-us/compliance/anz/pspf-tls-encryption?source=recommendations

Falzo · July 24

@Levi said:

REJECT with clear error message served is enough. Why support legacy? All big email providers use TLS 1.3. Everything else is irrelevant if not up to standard.

THIS!

rejecting is not losing. silently dropping would be.

manish · July 24

@Falzo said: rejecting is not losing. silently dropping would be.

This is a great way to proceed!

zed · July 24

what problem are you trying to solve

david · July 24

The point can be made that any encryption is better than none, since email can still generally be sent unencrypted.

That said, my mail servers are configured for minimum tls v1.1.

Good topic. I hadn't thought about this recently, and noticed I hadn't updated my settings for tls v1.3, yet.

manish · July 24

@zed said: what problem are you trying to solve

Do we have to worry even a bit when we configure our SMTP/MTA for a minimum of TLSv1.2, as both 1.0 and 1.1 have been deprecated since March 2021?

manish · July 24

@david said: That said, my mail servers are configured for minimum tls v1.1.

Thank you for the input. Version 1.1 is still relevant as per a few seasoned admins.

luckypenguin · July 24

TLSv1.2, TLSv1.3, never rejected anything important. Also not aware of any modern MTA that
will default to 1.0/1.1 when sending, so basically you shouldn't lose anything.

manish · July 24

@luckypenguin said: TLSv1.2, TLSv1.3, never rejected anything important.

Thank you for your input!

Sorry for a blunt response. How do you know? Do you monitor? If so, what % of transport use TLS 1.3 in your case?

With respect.

zed · July 24

@manish said:

@zed said: what problem are you trying to solve

Do we have to worry even a bit when we configure our SMTP/MTA for a minimum of TLSv1.2, as both 1.0 and 1.1 have been deprecated since March 2021?

i was too short, what i was implying is it's not a real issue.
what are you actually accomplishing with this change besides checking off a box?

personally i would rather leave it be than risk losing a single email.
the big mailers are going to have lots more stats than us so i'll follow their lead on this.
reject does sound ok except odds are the person seeing it will be confused.
edge cases are where you burn hours and i don't have any hours to spare.

i'm not saying you shouldn't do it, but some of my thoughts.

manish · July 24

@zed said: the big mailers are going to have lots more stats

If you follow 2 big email providers, Gmail supports it and Microsoft doesn't.
Local big provider Zoho supports it too.

Thank you for your thoughts. I appreciate it.

tommyluo · July 24

I think that depends on microsoft and google,if they both blocked it,then update you setting to be same,just like centos6,centos7,windows 2008,all out of date,but still many using these systems.

luckypenguin · July 24

@manish said: Sorry for a blunt response. How do you know? Do you monitor? If so, what % of transport use TLS 1.3 in your case?

Over 99% of legit emails were 1.3. I only receive proper RFC formatted mails and that means some misconfigured php mail() spam will be rejected anyway. As for spam I don't really care/monitor, chances are they use old compromised boxes with older TLS versions
if any encryption at all. All big corps default to 1.3, also all transactional mail providers
like Mailchimp and similar ones. I don't really expect anything from telco emails so no idea about what version they default to, but I would assume it's minimum 1.2.

manish · July 24

TLS for Mail: M3AAWG Baseline Recommendations

At this time, we recommend using only TLSv1.2 and TLSv1.3. Consistent with the IETF’s published guidance in RFC 8996, we recommend disabling earlier versions such as SSLv3, TLSv1, and TLSv1.1 due to the known security issues impacting protocols.

manish · July 24

@luckypenguin said: Over 99% of legit emails were 1.3.

good stats. do you run a relatively big server or is a personal server?

manish · July 24

@tommyluo said: centos6,centos7,windows 2008,all out of date,but still many using these systems.

Yes, correct. Just because something is deprecated doesn't mean it's technically unacceptable or dysfunctional immediately.

Mainfrezzer · July 24

If you need some legacy software to still work, just setup a proper smtp server that accepts your legacy submission (over a tunnel or just local) and then sends it proper with anything modern. Nothing can be that important that its send by a 90s dialup server.

luckypenguin · July 24

@manish said: do you run a relatively big server or is a personal server?

Just a personal server, that's why I can be pretty aggressive when it comes to filtering and
fine tuning. Even false positives/negatives are tolerable. Having said that, I dont think I rejected anything important, worst case it will go to spam when it shouldn't.

manish · July 24

@luckypenguin said: Just a personal server

Okay, and you are fine with >=TLSv1.2, correct?

I am sticking to Go's defaults as of yet basically supports TLS 1.0 but . I use TLS 1.3 + mTLS for auth with submissions/IMAPs [implicit TLS].

Although not a cool way to grade but my MX gets A+ here:
https://luxsci.com/smtp-tls-checker/

manish · July 24

@Mainfrezzer said: If you need some legacy software to still work, just setup a proper smtp server that accepts your legacy submission (over a tunnel or just local)

Great suggestion!

With smtp/MTA you don't know who you need to work with. Maybe this is why big providers still support older TLS protocols.

Thank you!

david · July 24

I think the big issue with tls 1.0/1.1 is poor quality ciphers. I have tls 1.1 enabled, but only for high quality ciphers:

PORT   STATE SERVICE VERSION
25/tcp open  smtp    Postfix smtpd
| ssl-enum-ciphers:
|   TLSv1.1:
|     ciphers:
|       TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA (ecdh_x25519) - A
|       TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (ecdh_x25519) - A
|     compressors:
|       NULL
|     cipher preference: server

jsg · July 24

I've seen exactly one comment here worth thinking about, the last one from @david.

I myself accept all email connections. Why?

email wasn't designed to be secure, it was designed to be reliable. Very different qualities.
if I need to exchange confidential data I simply use other means or, "worst case", encrypt them properly and send them as attachment.
most people do not even really know the history of SSL/TLS and don't know nor grasp why and what for it was created.
most people just use the cipher settings that come by default (incl. awful crap)
quite a few more points I can't be bothered to lay out

Btw., every version so far has later been found to be unsatisfying or even not really secure so far, while the vast majority of users was convinced to be totally safe. That will hold true for the current versions as well, sorry. Btw, greetings to the nsa.

manish · July 24

@david said: TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA

Don't the vulnerabilities come from the protocol-level implementation, not the cipher suite itself?

@jsg said: most people just use the cipher settings that come by default (incl. awful crap)

And with any reasonable MTA, it should go well, isn't it?

@jsg said: quite a few more points I can't be bothered to lay out

While we are at it, please jot them down for me.

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