use strict;
use warnings;
package Email::Sender::Manual::QuickStart 2.500;
# ABSTRACT: how to start using Email::Sender right now

#pod =head1 QUICK START
#pod
#pod =head2 Let's Send Some Mail!
#pod
#pod No messing around, let's just send some mail.
#pod
#pod   use strict;
#pod   use Email::Sender::Simple qw(sendmail);
#pod   use Email::MIME;
#pod
#pod   # You can make an email object in lots of ways.  Pick one you like!
#pod   my $email = Email::MIME->create(...);
#pod
#pod   sendmail($email);
#pod
#pod That's it.  Your message goes out into the internet and tries to get delivered
#pod to C<x.ample@example.com>.
#pod
#pod In the example above, C<$email> could be an Email::MIME object, a MIME::Entity,
#pod a string containing an email message, or one of several other types of input.
#pod If C<Email::Abstract> can understand a value, it can be passed to
#pod Email::Sender::Simple.  Email::Sender::Simple tries to make a good guess about
#pod how to send the message.  It will usually try to use the F<sendmail> program on
#pod unix-like systems and to use SMTP on Windows.  You can specify a transport, if
#pod you need to, but normally that shouldn't be an issue.  (See L</Picking a
#pod Transport>, though, for more information.)
#pod
#pod Also note that we imported and used a C<sendmail> routine in the example above.
#pod This is exactly the same as saying:
#pod
#pod   Email::Sender::Simple->send($email);
#pod
#pod ...but it's a lot easier to type.  You can use either one.
#pod
#pod =head3 envelope information
#pod
#pod We didn't have to tell Email::Sender::Simple where to send the message.  If you
#pod don't specify recipients, it will use all the email addresses it can find in
#pod the F<To> and F<Cc> headers by default.  It will use L<Email::Address> to parse
#pod those fields.  Similarly, if no sender is specified, it will use the first
#pod address found in the F<From> header.
#pod
#pod In most email transmission systems, though, the headers are not by necessity
#pod tied to the addresses used as the sender and recipients.  For example, your
#pod message header might say "From: mailing-list@example.com" while your SMTP
#pod client says "MAIL FROM:E<lt>verp-1234@lists.example.comE<gt>".  This is a
#pod powerful feature, and is necessary for many email application.  Being able to
#pod set those distinctly is important, and Email::Sender::Simple lets you do this:
#pod
#pod   sendmail($email, { to => [ $to_1, $to_2 ], from => $sender });
#pod
#pod =head3 in case of error
#pod
#pod When the message is sent successfully (at least on to its next hop),
#pod C<sendmail> will return a true value -- specifically, an
#pod L<Email::Sender::Success> object.  This object only rarely has much use.
#pod What's more useful is what happens if the message can't be sent.
#pod
#pod If there is an error sending the message, an exception will be thrown.  It will
#pod be an object belonging to the class L<Email::Sender::Failure>.  This object
#pod will have a C<message> attribute describing the nature of the failure.  There
#pod are several specialized forms of failure, like
#pod L<Email::Sender::Failure::Multi>, which is thrown when more than one error is
#pod encountered when trying to send.  You don't need to know about these to use
#pod Email::Sender::Simple, though.  All you need to know is that C<sendmail>
#pod returns true on success and dies on failure.
#pod
#pod If you'd rather not have to catch exceptions for failure to send mail, you can
#pod use the C<try_to_send> method, which can be imported as C<try_to_sendmail>.
#pod This method will return just false on failure to send mail.
#pod
#pod For example:
#pod
#pod   Email::Sender::Simple->try_to_send($email, { ... });
#pod
#pod   use Email::Sender::Simple qw(try_to_sendmail);
#pod   try_to_sendmail($email, { ... });
#pod
#pod Some Email::Sender transports can signal success if some, but not all,
#pod recipients could be reached.  Email::Sender::Simple does its best to ensure
#pod that this never happens.  When you are using Email::Sender::Simple, mail should
#pod either be sent or not.  Partial success should never occur.
#pod
#pod =head2 Picking a Transport
#pod
#pod =head3 passing in your own transport
#pod
#pod If Email::Sender::Simple doesn't pick the transport you want, or if you have
#pod more specific needs, you can specify a transport in several ways.  The simplest
#pod is to build a transport object and pass it in.  You can read more about
#pod transports elsewhere.  For now, we'll just assume that you need to send mail
#pod via SMTP on an unusual port.  You can send mail like this:
#pod
#pod   my $transport = Email::Sender::Transport::SMTP->new({
#pod     host => 'smtp.example.com',
#pod     port => 2525,
#pod   });
#pod
#pod   sendmail($email, { transport => $transport });
#pod
#pod Now, instead of guessing at what transport to use, Email::Sender::Simple will
#pod use the one you provided.  This transport will have to be specified for each
#pod call to C<sendmail>, so you might want to look at other options, which follow.
#pod
#pod =head3 specifying transport in the environment
#pod
#pod If you have a program that makes several calls to Email::Sender::Simple, and
#pod you need to run this program using a different mailserver, you can set
#pod environment variables to change the default.  For example:
#pod
#pod   $ export EMAIL_SENDER_TRANSPORT=SMTP
#pod   $ export EMAIL_SENDER_TRANSPORT_host=smtp.example.com
#pod   $ export EMAIL_SENDER_TRANSPORT_port=2525
#pod
#pod   $ perl your-program
#pod
#pod It is important to note that if you have set the default transport by using the
#pod environment, I<< no subsequent C<transport> args to C<sendmail> will be
#pod respected >>.  If you set the default transport via the environment, that's it.
#pod Everything will use that transport.  (Also, note that while we gave the host and
#pod port arguments above in lower case, the casing of arguments in the environment
#pod is flattened to support systems where environment variables are of a fixed
#pod case.  So, C<EMAIL_SENDER_TRANSPORT_PORT> would also work.
#pod
#pod This is extremely valuable behavior, as it allows you to audit every message
#pod that would be sent by a program by running something like this:
#pod
#pod   $ export EMAIL_SENDER_TRANSPORT=Maildir
#pod   $ perl your-program
#pod
#pod In that example, any message sent via Email::Sender::Simple would be delivered
#pod to a maildir in the current directory.
#pod
#pod =head3 subclassing to change the default transport
#pod
#pod If you want to use a library that will behave like Email::Sender::Simple but
#pod with a different default transport, you can subclass Email::Sender::Simple and
#pod replace the C<build_default_transport> method.
#pod
#pod =head2 Testing
#pod
#pod Email::Sender::Simple makes it very, very easy to test code that sends email.
#pod The simplest way is to do something like this:
#pod
#pod   use Test::More;
#pod   BEGIN { $ENV{EMAIL_SENDER_TRANSPORT} = 'Test' }
#pod   use YourCode;
#pod
#pod   YourCode->run;
#pod
#pod   my @deliveries = Email::Sender::Simple->default_transport->deliveries;
#pod
#pod Now you've got an array containing every delivery performed through
#pod Email::Sender::Simple, in order.  Because you set the transport via the
#pod environment, no other code will be able to force a different transport.
#pod
#pod When testing code that forks, L<Email::Sender::Transport::SQLite> can be used
#pod to allow every child process to deliver to a single, easy to inspect
#pod destination database.
#pod
#pod =head2 Hey, where's my Bcc support?
#pod
#pod A common question is "Why doesn't Email::Sender::Simple automatically respect
#pod my Bcc header?"  This is often combined with, "Here is a patch to 'fix' it."
#pod This is not a bug or oversight. Bcc is being ignored intentionally for now
#pod because simply adding the Bcc addresses to the message recipients would not
#pod produce the usually-desired behavior.
#pod
#pod For example, here is a set of headers:
#pod
#pod   From: sender@example.com
#pod   To:   to_rcpt@example.com
#pod   Cc:   cc_rcpt@example.com
#pod   Bcc:  the_boss@example.com
#pod
#pod In this case, we'd expect the message to be delivered to three people:
#pod to_rcpt, cc_rcpt, and the_boss.  This is why it's often suggested that the
#pod Bcc header should be a source for envelope recipients.  In fact, though, a
#pod message with a Bcc header should probably be delivered I<only> to the Bcc
#pod recipients.  The "B" in Bcc means "blind."  The other recipients should not
#pod see who has been Bcc'd.  This means you want to send I<two> messages:  one to
#pod to_rcpt and cc_rcpt, with no Bcc header present; and another to the_boss
#pod only, with the Bcc header.  B<If you just pick up Bcc addresses as
#pod recipients, everyone will see who was Bcc'd.>
#pod
#pod Email::Sender::Simple promises to send messages atomically.  That is:  it
#pod won't deliver to only some of the recipients, and not to others.  That means
#pod it can't automatically detect the Bcc header and make two deliveries.  There
#pod would be a possibility for the second to fail after the first succeeded,
#pod which would break the promise of a pure failure or success.
#pod
#pod The other strategy for dealing with Bcc is to remove the Bcc header from the
#pod message and then inject the message with an envelope including the Bcc
#pod addresses.  The envelope information will not be visible to the final
#pod recipients, so this is safe.  Unfortunately, this requires modifying the
#pod message, and Email::Sender::Simple should not be altering the mutable email
#pod object passed to it.  There is no C<clone> method on Email::Abstract, so it
#pod cannot just build a clone and modify that, either.  When such a method
#pod exists, Bcc handling may be possible.
#pod
#pod =head3 Example Bcc Handling
#pod
#pod If you want to support the Bcc header now, it is up to you to deal with how
#pod you want to munge the mail and inject the (possibly) munged copies into your
#pod outbound mailflow.  It is not reasonable to suggest that
#pod Email::Sender::Simple do this job.
#pod
#pod =head4 Example 1: Explicitly set the envelope recipients for Bcc recipients
#pod
#pod Create the email without a Bcc header, send it to the Bcc users explicitly
#pod and then send it to the To/Cc users implicitly.
#pod
#pod   my $message = create_email_mime_msg;  # <- whatever you do to get the message
#pod
#pod   $message->header_set('bcc');          # delete the Bcc header before sending
#pod   sendmail($message, { to => $rcpt });  # send to explicit Bcc address
#pod   sendmail($message);                   # and then send as normal
#pod
#pod =head4 Example 2: Explicitly set the envelope recipients for all recipients
#pod
#pod You can make a single call to C<sendmail> by pulling all the recipient
#pod addresses from the headers yourself and specifying all the envelope
#pod recipients once.  Again, delete the Bcc header before the message is sent.
#pod
#pod =head1 SEE ALSO
#pod
#pod =head2 This is awesome!  Where can I learn more?
#pod
#pod Have a look at L<Email::Sender::Manual>, where all the manual's documents are
#pod listed.  You can also look at the documentation for L<Email::Sender::Simple>
#pod and the various Email::Sender::Transport classes.
#pod
#pod =cut

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Email::Sender::Manual::QuickStart - how to start using Email::Sender right now

=head1 VERSION

version 2.500

=head1 PERL VERSION

This library should run on perls released even a long time ago.  It should work
on any version of perl released in the last five years.

Although it may work on older versions of perl, no guarantee is made that the
minimum required version will not be increased.  The version may be increased
for any reason, and there is no promise that patches will be accepted to lower
the minimum required perl.

=head1 QUICK START

=head2 Let's Send Some Mail!

No messing around, let's just send some mail.

  use strict;
  use Email::Sender::Simple qw(sendmail);
  use Email::MIME;

  # You can make an email object in lots of ways.  Pick one you like!
  my $email = Email::MIME->create(...);

  sendmail($email);

That's it.  Your message goes out into the internet and tries to get delivered
to C<x.ample@example.com>.

In the example above, C<$email> could be an Email::MIME object, a MIME::Entity,
a string containing an email message, or one of several other types of input.
If C<Email::Abstract> can understand a value, it can be passed to
Email::Sender::Simple.  Email::Sender::Simple tries to make a good guess about
how to send the message.  It will usually try to use the F<sendmail> program on
unix-like systems and to use SMTP on Windows.  You can specify a transport, if
you need to, but normally that shouldn't be an issue.  (See L</Picking a
Transport>, though, for more information.)

Also note that we imported and used a C<sendmail> routine in the example above.
This is exactly the same as saying:

  Email::Sender::Simple->send($email);

...but it's a lot easier to type.  You can use either one.

=head3 envelope information

We didn't have to tell Email::Sender::Simple where to send the message.  If you
don't specify recipients, it will use all the email addresses it can find in
the F<To> and F<Cc> headers by default.  It will use L<Email::Address> to parse
those fields.  Similarly, if no sender is specified, it will use the first
address found in the F<From> header.

In most email transmission systems, though, the headers are not by necessity
tied to the addresses used as the sender and recipients.  For example, your
message header might say "From: mailing-list@example.com" while your SMTP
client says "MAIL FROM:E<lt>verp-1234@lists.example.comE<gt>".  This is a
powerful feature, and is necessary for many email application.  Being able to
set those distinctly is important, and Email::Sender::Simple lets you do this:

  sendmail($email, { to => [ $to_1, $to_2 ], from => $sender });

=head3 in case of error

When the message is sent successfully (at least on to its next hop),
C<sendmail> will return a true value -- specifically, an
L<Email::Sender::Success> object.  This object only rarely has much use.
What's more useful is what happens if the message can't be sent.

If there is an error sending the message, an exception will be thrown.  It will
be an object belonging to the class L<Email::Sender::Failure>.  This object
will have a C<message> attribute describing the nature of the failure.  There
are several specialized forms of failure, like
L<Email::Sender::Failure::Multi>, which is thrown when more than one error is
encountered when trying to send.  You don't need to know about these to use
Email::Sender::Simple, though.  All you need to know is that C<sendmail>
returns true on success and dies on failure.

If you'd rather not have to catch exceptions for failure to send mail, you can
use the C<try_to_send> method, which can be imported as C<try_to_sendmail>.
This method will return just false on failure to send mail.

For example:

  Email::Sender::Simple->try_to_send($email, { ... });

  use Email::Sender::Simple qw(try_to_sendmail);
  try_to_sendmail($email, { ... });

Some Email::Sender transports can signal success if some, but not all,
recipients could be reached.  Email::Sender::Simple does its best to ensure
that this never happens.  When you are using Email::Sender::Simple, mail should
either be sent or not.  Partial success should never occur.

=head2 Picking a Transport

=head3 passing in your own transport

If Email::Sender::Simple doesn't pick the transport you want, or if you have
more specific needs, you can specify a transport in several ways.  The simplest
is to build a transport object and pass it in.  You can read more about
transports elsewhere.  For now, we'll just assume that you need to send mail
via SMTP on an unusual port.  You can send mail like this:

  my $transport = Email::Sender::Transport::SMTP->new({
    host => 'smtp.example.com',
    port => 2525,
  });

  sendmail($email, { transport => $transport });

Now, instead of guessing at what transport to use, Email::Sender::Simple will
use the one you provided.  This transport will have to be specified for each
call to C<sendmail>, so you might want to look at other options, which follow.

=head3 specifying transport in the environment

If you have a program that makes several calls to Email::Sender::Simple, and
you need to run this program using a different mailserver, you can set
environment variables to change the default.  For example:

  $ export EMAIL_SENDER_TRANSPORT=SMTP
  $ export EMAIL_SENDER_TRANSPORT_host=smtp.example.com
  $ export EMAIL_SENDER_TRANSPORT_port=2525

  $ perl your-program

It is important to note that if you have set the default transport by using the
environment, I<< no subsequent C<transport> args to C<sendmail> will be
respected >>.  If you set the default transport via the environment, that's it.
Everything will use that transport.  (Also, note that while we gave the host and
port arguments above in lower case, the casing of arguments in the environment
is flattened to support systems where environment variables are of a fixed
case.  So, C<EMAIL_SENDER_TRANSPORT_PORT> would also work.

This is extremely valuable behavior, as it allows you to audit every message
that would be sent by a program by running something like this:

  $ export EMAIL_SENDER_TRANSPORT=Maildir
  $ perl your-program

In that example, any message sent via Email::Sender::Simple would be delivered
to a maildir in the current directory.

=head3 subclassing to change the default transport

If you want to use a library that will behave like Email::Sender::Simple but
with a different default transport, you can subclass Email::Sender::Simple and
replace the C<build_default_transport> method.

=head2 Testing

Email::Sender::Simple makes it very, very easy to test code that sends email.
The simplest way is to do something like this:

  use Test::More;
  BEGIN { $ENV{EMAIL_SENDER_TRANSPORT} = 'Test' }
  use YourCode;

  YourCode->run;

  my @deliveries = Email::Sender::Simple->default_transport->deliveries;

Now you've got an array containing every delivery performed through
Email::Sender::Simple, in order.  Because you set the transport via the
environment, no other code will be able to force a different transport.

When testing code that forks, L<Email::Sender::Transport::SQLite> can be used
to allow every child process to deliver to a single, easy to inspect
destination database.

=head2 Hey, where's my Bcc support?

A common question is "Why doesn't Email::Sender::Simple automatically respect
my Bcc header?"  This is often combined with, "Here is a patch to 'fix' it."
This is not a bug or oversight. Bcc is being ignored intentionally for now
because simply adding the Bcc addresses to the message recipients would not
produce the usually-desired behavior.

For example, here is a set of headers:

  From: sender@example.com
  To:   to_rcpt@example.com
  Cc:   cc_rcpt@example.com
  Bcc:  the_boss@example.com

In this case, we'd expect the message to be delivered to three people:
to_rcpt, cc_rcpt, and the_boss.  This is why it's often suggested that the
Bcc header should be a source for envelope recipients.  In fact, though, a
message with a Bcc header should probably be delivered I<only> to the Bcc
recipients.  The "B" in Bcc means "blind."  The other recipients should not
see who has been Bcc'd.  This means you want to send I<two> messages:  one to
to_rcpt and cc_rcpt, with no Bcc header present; and another to the_boss
only, with the Bcc header.  B<If you just pick up Bcc addresses as
recipients, everyone will see who was Bcc'd.>

Email::Sender::Simple promises to send messages atomically.  That is:  it
won't deliver to only some of the recipients, and not to others.  That means
it can't automatically detect the Bcc header and make two deliveries.  There
would be a possibility for the second to fail after the first succeeded,
which would break the promise of a pure failure or success.

The other strategy for dealing with Bcc is to remove the Bcc header from the
message and then inject the message with an envelope including the Bcc
addresses.  The envelope information will not be visible to the final
recipients, so this is safe.  Unfortunately, this requires modifying the
message, and Email::Sender::Simple should not be altering the mutable email
object passed to it.  There is no C<clone> method on Email::Abstract, so it
cannot just build a clone and modify that, either.  When such a method
exists, Bcc handling may be possible.

=head3 Example Bcc Handling

If you want to support the Bcc header now, it is up to you to deal with how
you want to munge the mail and inject the (possibly) munged copies into your
outbound mailflow.  It is not reasonable to suggest that
Email::Sender::Simple do this job.

=head4 Example 1: Explicitly set the envelope recipients for Bcc recipients

Create the email without a Bcc header, send it to the Bcc users explicitly
and then send it to the To/Cc users implicitly.

  my $message = create_email_mime_msg;  # <- whatever you do to get the message

  $message->header_set('bcc');          # delete the Bcc header before sending
  sendmail($message, { to => $rcpt });  # send to explicit Bcc address
  sendmail($message);                   # and then send as normal

=head4 Example 2: Explicitly set the envelope recipients for all recipients

You can make a single call to C<sendmail> by pulling all the recipient
addresses from the headers yourself and specifying all the envelope
recipients once.  Again, delete the Bcc header before the message is sent.

=head1 SEE ALSO

=head2 This is awesome!  Where can I learn more?

Have a look at L<Email::Sender::Manual>, where all the manual's documents are
listed.  You can also look at the documentation for L<Email::Sender::Simple>
and the various Email::Sender::Transport classes.

=head1 AUTHOR

Ricardo Signes <rjbs@semiotic.systems>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2021 by Ricardo Signes.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut
