Re: [PATCH v2] send-email: add --get-smtp-server option to fetch SMTP settings

> Hi Aditya, really cool idea, here are some random thoughts:
> 
> On Wed Jul 30, 2025 at 5:12 PM CEST, Aditya Garg wrote:
>> Autoconfiguring SMTP server settings is a common feature present in many
>> email clients. In order to get the correct SMTP server settings easily,
>> this commit adds a `--get-smtp-server` option to `git send-email`. This
>> option attempts to fetch the SMTP server settings for a given email address
>> via the following steps:
>> 
>> 1. It first tries to fetch the settings from Mozilla's ISPDB at
>>   `https://autoconfig.thunderbird.net/v1.1/[domain]`.
> 
> We should first check autoconfig and then move to the 3rd party
> database, this is how thunderbird[0] and aerc[1] do it.

> 
>> 
>> 2. If that fails, it attempts to fetch the autoconfig file from the email
>>   provider's autoconfig URL, which is typically in the format
>>   `https://autoconfig.[domain]/mail/config-v1.1.xml?emailaddress=[email]`.
> 
> The documentation mentions using `DOMAIN/.well-known/autoconfig/mail/`
> as an alternative to the autoconfig subdomain, what do you think about
> supporting that?

> 
>> 
>> 3. If that also fails, it falls back to checking the MX records of the
>>   domain used in the email address to find the SMTP server. It can be
>>   useful in case of emails with custom domains. It attempts to guess
>>   the correct domain for the email from the MX records, and repeats the
>>   first 2 steps with the guessed domain.
>> 
>> This feature is heavily inpired by the autoconfig feature in Mozilla
> 
> s/inpired/inspired

> 
> 
>> +sub parse_config {
>> +	require XML::LibXML;
>> +	my ($xml, $email) = @_;
>> +	my $parser = XML::LibXML->new;
>> +	my $doc = eval { $parser->load_xml(string => $xml) };
>> +	die "Failed to parse XML\n" unless $doc;
>> +	my $config_num = 0;
>> +	my $smtp_encryption_config;
>> +	my $smtp_user_config;
>> +
>> +	foreach my $outgoing ($doc->findnodes('//outgoingServer')) {
>> +		$config_num++;
>> +		if ($outgoing->findvalue('./socketType') eq 'SSL') {
>> +			$smtp_encryption_config = 'ssl';
>> +		} elsif ($outgoing->findvalue('./socketType') eq 'STARTTLS') {
>> +			$smtp_encryption_config = 'tls';
>> +		} else {
>> +			$smtp_encryption_config = 'plain';
> 
> 'plain' is unencrypted, I think this should be accompanied by a big
> warning.

> 
>> +		}
>> +
>> +		if ($outgoing->findvalue('./username') eq '%EMAILADDRESS%') {
>> +			$smtp_user_config = $email;
>> +		} elsif ($outgoing->findvalue('./username') eq '%EMAILLOCALPART%') {
>> +			$smtp_user_config = (split /@/, $email)[0];
>> +		} elsif ($outgoing->findvalue('./username') eq '%EMAILDOMAIN%') {
>> +			$smtp_user_config = (split /@/, $email)[1];
>> +		} else {
>> +			$smtp_user_config = $outgoing->findvalue('./username');
>> +		}
>> +
>> +		print "\nConfiguration $config_num:\n";
>> +		print "  Server: ", $outgoing->findvalue('./hostname'), "\n";
>> +		print "  Port: ", $outgoing->findvalue('./port'), "\n";
>> +		print "  Encryption: ", $smtp_encryption_config, "\n";
>> +		print "  Username: ", $smtp_user_config, "\n";
> 
> The new option only gives you the needed SMTP configuration, as a
> user you still need to apply them and to do that you will need to
> look up how. We could help the user here and give them copy and
> paste commands similar to when trying to commit without having an
> identity set.

> 
>> +	}
>> +}
>> +
>> +if ($get_smtp_server) {
>> +	require URI::Escape;
>> +	print "Enter your email address: ";
>> +	chomp(my $email = <STDIN>);
> 
> Someone sending out emails will most likely already have set up
> `user.email` in their gitconfig. We could just use that instead of
> prompting for user input, or at least suggest it as a default.

> If you don't have an SMTP server configured then `git send-email`
> will default to `localhost` and fail if you are not running a
> local SMTP server with: `Unable to initialize SMTP properly.
> Check config and use --smtp-debug.`. I would suggest altering the
> message pointing the user to the new option.