Autoconfig is broken

[phormanns]

• Operating System: Linux (Debian Bookworm)
• Core Version: v2.9.0
• Client Version: Delta Chat Desktop 2.9.0 (Tauri)

also tested on:

• Operating System: Android 13
• Core Version: 1.58.4 ?
• Client Version: Delta Chat 1.58.4-foss

Expected behavior

I try to add a new profile. In german:

1. "Neues Profil erstellen"
2. "Anderen Server verwenden"
3. "Klassischer E-Mail-Login"
4. Enter EMail-Address "test@chat.example.com" and Password
5. Client should try autoconfig per HTTP GET request on "https://chat.example.com/.well-known/autoconfig/mail/config-v1.1.xml?emailaddress=test@chat.jalin.de"

Actual behavior

6. Client URL ist missing the parameter "emailaddress=test@chat.example.com" and gets an HTTP/400 response.
7. The client attempts to guess an SMTP and IMAP server. That fails.

Steps to reproduce the problem

see above

Logs

HTTP Server Log
chat.example.com 199.99.99.199 - - [06/Aug/2025:15:29:04 +0200] "GET /.well-known/autoconfig/mail/config-v1.1.xml HTTP/1.1" 400 3341 "-" "-"

An expected request with curl shows:
chat.example.com 199.99.99.199 - - [06/Aug/2025:15:39:18 +0200] "GET /.well-known/autoconfig/mail/config-v1.1.xml?emailaddress=test%40chat.example.com HTTP/2.0" 200 808 "-" "curl/7.88.1"

[link2xt]

According to https://datatracker.ietf.org/doc/draft-ietf-mailmaint-autoconfig/03/ emailaddress is only used for autoconfig subdomain, but not for .well-known URL. This is how we implement it. I opened an issue benbucksch/autoconfig-spec#17 because it is not clear if emailaddress argument is not included in .well-known URLs on purpose.

Thunderbird seems to send emailaddress to both URLs according to https://hg-edge.mozilla.org/comm-central/file/757a86e8931e48c05f8f0449bc6647c5d4c3dfa8/mail/components/accountcreation/modules/FetchConfig.sys.mjs

Is this your server? Are you using some existing email server software?

Specification has a section "Customzing the config for a specific user" that says customizing configs on the server is discouraged and static file with placeholders should be preferred.

[tpokorra]

I am a colleague of @phormanns
We are trying to get DeltaChat to work with the autoconfig provided by our servers at Hostsharing.

I have now tried to implement the autoconfig subdomain:

https://autoconfig.pokorra.de/mail/config-v1.1.xml?emailaddress=testdelta%40pokorra.de

This seems to look ok.

But in DeltaChat Desktop, I still get:

17s [i]core/event: 15 src/configure.rs:378: No offline autoconfig found.
17s [i]core/event: 15 src/net/http.rs:322: Not found "https://autoconfig.pokorra.de/mail/config-v1.1.xml?emailaddress=testdelta%40pokorra.de" in cache, fetching.
17s [i]core/event: 15 src/net/dns.rs:140: No memory-cached DNS resolution for autoconfig.pokorra.de available, waiting for the resolver.
17s [D]core/event: 15 NewBlobFile {
  file: '$BLOBDIR/91f9bc261758b09b57844798ebb61f1.jpg',
  kind: 'NewBlobFile'
}
17s [i]core/event: 15 src/net/dns.rs:180: Resolved autoconfig.pokorra.de into 2a01:37:1000::53df:4f75:0.
17s [i]core/event: 15 src/net/dns.rs:180: Resolved autoconfig.pokorra.de into 83.223.79.117.
17s [i]core/event: 15 src/chat.rs:2804: Attaching "/home/timotheus/.config/DeltaChat/accounts/40abcfb6-3b44-46ae-9f34-7a673003f839/dc.db-blobs/91f9bc261758b09b57844798ebb61f1.jpg" for message type #Image.
17s [D]core/event: 15 MsgsChanged { chatId: 11, kind: 'MsgsChanged', msgId: 10 }
17s [D]core/event: 15 ChatlistChanged { kind: 'ChatlistChanged' }
17s [D]core/event: 15 ChatlistItemChanged { chatId: 11, kind: 'ChatlistItemChanged' }
17s [D]core/event: 15 MsgsChanged { chatId: 11, kind: 'MsgsChanged', msgId: 11 }
17s [D]core/event: 15 ChatlistChanged { kind: 'ChatlistChanged' }
17s [D]core/event: 15 ChatlistItemChanged { chatId: 11, kind: 'ChatlistItemChanged' }
17.1s [D]core/event: 15 ConfigureProgress { comment: null, kind: 'ConfigureProgress', progress: 300 }
17.1s [i]core/event: 15 src/net/http.rs:322: Not found "https://pokorra.de/.well-known/autoconfig/mail/config-v1.1.xml?emailaddress=testdelta%40pokorra.de" in cache, fetching.
17.1s [i]core/event: 15 src/net/dns.rs:140: No memory-cached DNS resolution for pokorra.de available, waiting for the resolver.

We are no experts in Rust, and found the code here:
https://github.com/chatmail/core/blob/main/src/configure.rs#L613
This looks to me, as if the parameter emailaddress is used for both autoconfig subdomain and .well-known.
Or is the desktop client using different code?

[link2xt]

I made a fix: #7086

The problem was indeed that URL query parameters were not sent.

[phormanns]

In many cases, an autoconfig service can serve a static XML file with variables %emailaddress% or %localpart%. However, the IMAP login cannot generally be derived from the email address. In this case, the autoconfig service requires the email address as a parameter in order to specify the correct mailbox.
Thank you for your quick response!