This appendix discusses post.office's compatibility with sendmail: Functional & command line compatibility Command line switches and options
SENDMAIL COMPATIBILITY

• F.0 SENDMAIL COMPATIBILITY
• F.1 SENDMAIL AND POST.OFFICE
  • Functional Compatibility
  • SMTP
  • Incoming
  • Outgoing
  • Aliases
  • Delivery to Programs
  • Delivery to Files
  • Mailing Lists
  • Command Line Compatibility
  • Sending Mail with the sendmail Replacement
  • Starting post.office with sendmail
  • Checking the Mail Queue
  • Other Modes
• F.2 REFERENCE: COMMAND-LINE SWITCHES AND OPTIONS
  • Alternate Names for sendmail
  • Command-Line Switches
  • sendmail Options

F.0 SENDMAIL COMPATIBILITY

This appendix is directed towards system administrators who are thinking about or have made the switch from sendmail to post.office.

The first section discusses the replacement sendmail program provided with post.office for compatibility with UNIX systems. The second section is a comprehensive list of command-line switches and configuration options is included along with their effects on post.office behavior.

We intend to keep this compatibility section current. However it is possible that new functionality will be added to post.office that makes it more compatible with sendmail than is noted here. If you find that you require some missing functionality, let us know so we can schedule it for a future release.

F.1 SENDMAIL AND POST.OFFICE

This section discusses the compatibility between sendmail and post.office:

First the functional compatibility section discusses how things you can do with sendmail are done with post.office.

Following, the command-line compatibility of the replacement sendmail program is outlined.

FUNCTIONAL COMPATIBILITY

SMTP NETWORK INTERFACE

The sendmail program can be configured to exchange mail with remote destinations using SMTP. Routing of mail is achieved with rule sets containing address production rules which are written in a specialized programming language used to rip apart addresses and put them back together in useful ways. While this is a very powerful facility, it is error-prone and requires extensive knowledge of Internet standards to be set up correctly.

In contrast, post.office comes with a pre-configured SMTP channel for interacting with other machines on the Internet. It works off-the-shelf, so you don't have to become an expert just to send and receive mail. If you have any special routing requirements, post.office provides channel aliases and a mail routing table which should cover those needs. They are easy to set up (refer to operations chapters for details regarding these features). The following two sections describe mail flow through the SMTP channel of post.office.

Incoming

Incoming mail is received by the SMTP-Accept module of post.office. Its job is to read in one or more messages from a remote mail server and store them in the message queue. For each incoming message, SMTP-Accept invokes the SMTP-Router to decide how to route the message to its destination.

Outgoing

Any message that the SMTP-Router decides needs to be delivered using SMTP to a remote site is given to the SMTP-Deliver module. This module contacts the destination computer (actually one of its mail exchangers) and delivers the message. If for some reason delivery fails, the message remains queued for a later attempt or is returned (if the error is considered permanent).

ALIASES AND MAIL FORWARDING

The sendmail program supports several types of aliases in the /etc/aliases file and users' personal .forward files. The various types of aliases allow:

• a local user to receive mail at several addresses
• a message to be distributed to multiple recipients
• a message to be forwarded to a user(s) at another machine(s)

With post.office each type of alias is created differently. This is due to the structure of user accounts in the account database. The use of accounts and aliases is discussed at length in chapter 4.

DELIVERY TO PROGRAMS

Using sendmail, it is possible to create an alias or forward that delivers an incoming message to a program. The program then reads the message and performs some operation depending on the message contents. Usually these types of programs are used to filter messages into different mailboxes, or to send out vacation notices. This functionality makes it easy to extend the mail system to do virtually anything you want, but has been problematic with respect to security. post.office program delivery is set up using the account form.

Because there are security issues specific to program delivery, program delivery is disabled by default. For a discussion of the security issues and instructions on how to enable program delivery, refer to appendix G.

DELIVERY TO FILES

The sendmail program makes it possible to set up an alias or .forward file to append mail to a file. This can be used to keep a record of incoming mail, or to delete it (by sending it to /dev/null). However, the author of sendmail recommends using an alternate delivery agent for delivery-to-file needs, invoked via the delivery-to-program facility.

The sendmail replacement that comes with post.office will append undeliverable messages to users' dead.letter files. No general delivery-to-file facility is planned for post.office; appending mail to a file should be done with the delivery-to-program facility.

MAILING LISTS

Mailing lists in sendmail are implemented using aliases and program deliveries. List recipients are stored either in the aliases database or in an external file using an :include: alias. Several mailing list administration programs are available that can automate the task of maintaining the recipient distribution list(s), while sendmail handles the delivery of the messages.

post.office has "hooks" to handle mailing lists. Delivering messages to a list of recipients is something post.office does well. However there are some other special requirements of mailing list exploders that are not yet implemented. Also, Automating the administration tasks is an interesting and difficult problem to solve. (There are many deficiencies in currently available mailing list administration programs that we are in the process of reviewing.) As with the rest of post.office, we will insure that mailing lists are as easy to set up and maintain as normal accounts.

COMMAND LINE COMPATIBILITY

The post.office mail system includes a program which replaces /usr/lib/sendmail on UNIX machines. Most of sendmail's functionality is performed by one or more modules in post.office as noted above, so the sendmail replacement actually has limited use. However, it is needed for compatibility with many mail programs that employ sendmail to deliver their mail, rather than using SMTP. It can also be used to start up the post.office mail system, and check and deliver the mail queue.

SENDING MAIL WITH THE SENDMAIL REPLACEMENT

Probably the most important reason to have a replacement sendmail program is to maintain compatibility with existing software that delivers mail using the sendmail command. This software runs the sendmail command and feeds it the message to be delivered. It is then left up to sendmail to deliver the message to all the recipients.

Some examples of commands that work for sending mail are:

/usr/lib/sendmail -t < /tmp/message

cat file1 | /usr/lib/sendmail -oem recip1,recip2

For a complete list of command-line switches and options related to sending mail, see the reference section below (F.2).

STARTING POST.OFFICE WITH SENDMAIL

Since sendmail comes installed on most UNIX-based machines, many scripts such as system boot scripts exist to start up sendmail. This is done with a command like:

/usr/lib/sendmail -bd -q30m

The sendmail replacement provided with post.office recognizes this and starts up post.office if it is not already running. The -q30m switch is ignored in this command since queue intervals are set up in the system configuration of post.office.

CHECKING THE MAIL QUEUE

Many system administrators are used to typing 'mailq' to check for queued messages. The sendmail replacement provided with post.office will respond to this command with the contents of the mail queue.

However, many users prefer to use the post.office mail queue form, which makes processing the queue a little easier.

OTHER MODES

The sendmail program has several other operating modes which are not necessary or are not supported in post.office. For a complete list of supported operating modes, command-line switches and options, see the reference section below.

F.2 REFERENCE:

This reference section lists all the available command-line arguments the sendmail replacement program recognizes, along with the behavior that can be expected when they are used. Certain options are recognized (via the -o command-line switch) and their effects are noted in a separate table.

ALTERNATE NAMES FOR SENDMAIL

The sendmail program can be run under several names as a shorthand way to specify the action to perform. The sendmail replacement program recognizes several alternate names. The behavior that results from invoking the sendmail replacement with one of the alternate names is summarized in the following table.

Table F.1 Alternate Behavior of sendmail Replacement

It is important to note that the behavior listed in the above table is the behavior that will result if no other behavior is specified using a command-line option such as -b or -I.

Command-line switches are processed using getopt(3) as in V8 sendmail. All of the switches supported by V8 sendmail, IDA sendmail and other versions of sendmail are recognized, and the extent of support for these switches is given in the following table.

Table F.2 Supported command-line switches

SENDMAIL OPTIONS

The sendmail replacement provided with post.office does not need a configuration file (sendmail.cf), yet most of sendmail's options can be set from the command line. Many of the options are meant for the sendmail daemon, but some of them are relevant to the normal operation of sending mail.

All of the options supported by V8 sendmail are recognized and the extent of the support for these options is shown below. Note that the options below only refer to the replacement sendmail program, not to post.office as a whole. Many of the options not supported by the sendmail replacement are supported by post.office in one way or another. Refer to the relevant sections of the manual to determine how to set parameters within post.office.

Table F.3 sendmail options as they are supported and affect the post.office sendmail program.