Somewhat tangential... clients automatically detecting correct config settings

Dilyan Palauzov Dilyan.Palauzov at
Mon Jun 11 08:00:31 EDT 2018


apart from SRV DNS records for _imap._tcp and _submit._tcp  
(, Thunderbird assumes,  
that email local part != username, so there is the autoconfig stuff:

With it the client can extract from the email address not only the  
servers and ports, but also the user name.
See also the linked pages.  This is used also by other clients, but I  
cannot tell you which.

For Outlook there is different approach.  Automx  
[] tries to offer something, which both  
Thunderbird and Outlook can use.

Have fun
----- Message from Dan White <dwhite at> ---------
    Date: Sun, 10 Jun 2018 19:06:53 -0500
    From: Dan White <dwhite at>
Subject: Re: Somewhat tangential...  clients automatically detecting  
correct config settings
      To: Philip Prindeville <philipp_subx at>
      Cc: Cyrus Devel <cyrus-devel at>

> On 06/10/18 17:00 -0600, Philip Prindeville wrote:
>> Hi.
>> I was wondering how do popular clients (like detect what  
>> the settings should be for an email client when you initially enter  
>> the email address.
>> Does anyone know how it tries to detect this stuff?
>> I’m trying to set up my email server so that users don’t need to go  
>> through the painful manual configuration.
>> Thanks,
>> -Philip
> This is Thunderbird's approach:
> /**
> * Try to guess the config, by:
> * - guessing hostnames (pop3.<domain>, pop.<domain>, imap.<domain>,
> *                       mail.<domain> etc.)
> * - probing known ports (for IMAP, POP3 etc., with SSL, STARTTLS etc.)
> * - opening a connection via the right protocol and checking the
> *   protocol-specific CAPABILITIES like that the server returns.
> *
> * Final verification is not done here, but in verifyConfig().
> ...
> See: mailnews/base/prefs/content/accountcreation/guessConfig.js in the
> source.

----- End message from Dan White <dwhite at> -----

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