Sendmail basic information For most systems, this is probably the only form you will have to com- plete to get email working. This configuration generally differenti- ates email servers from "client" workstations. 11.. BBaassee iinnffoo You enter the information here that is required to accept and deliver mail properly. 11..11.. PPrreesseenntt yyoouurr ssyysstteemm aass Even if email can come from different machines in your organization, you may want to hide this fact and present email as if it was from a single machine or domain. This field is normally used in most setups and simply contains your official domain name. 11..22.. AAcccceepptt eemmaaiill ffoorr ""yyoouurr ddoommaaiinn"" If you are configuring the main server of an organization, you must check this field as "on." Normally, a sendmail server will accept only email sent to its fully qualified host name. If this is the main server, it will generally receive email addressed to the domain, not the server's name. Checking this box allows the server to accept both as equivalent. For example, if your domain is foo.com and your server is mail.foo.com, then mail to joe@foo.com and mail to joe@mail.foo.com will be accepted and stored locally on this server (if user joe exists). 11..33.. MMaaiill sseerrvveerr In most organizations, there is one machine which stores email for all users, even if the email originated from different machines. _U_N_I_X machines are multi-user. It is possible for a user to send email to other users on this machine. The default behavior is to store the message in the mail folder of the user on this machine. This is often inappropriate. _U_N_I_X machines are not only multi-user, but network oriented. This user (the recipient) may very well have accounts on many machines on the network (often on all machines) and may elect to read email messages on another machine. Having his email messages distributed onto different machines on the network is not useful. Instead, specify the fully qualified name of the mail server of the organization, and all email messages will be forward to it. 11..44.. MMaaiill ggaatteewwaayy Most machines on a network lack the connectivity to forward email properly. So, you can specify the name of a machine which knows better. In many organizations, this machine is often the mail server. Unlike the mail server, the mail gateway may be reached by different mailer transport/protocols such as ESMTP and UUCP. 11..55.. MMaaiill ggaatteewwaayy pprroottooccooll You must specify how to reach the mail gateway. If you choose ESMTP, then you must specify a fully qualified name for the mail gateway. If you specify UUCP, then you must specify a uucp name for the mail gateway. For on-demand Internet connections, the "expensive ESMTP" protocol is probably what you want. It queues all out-going mail. To deliver queued mail, you issue (using either scheduled tasks(cron) or the "process queue every (minutes)" field) a delivery command, which processes the queue. 22.. FFeeaattuurreess 22..11.. MMaattcchh ffuullll uusseerr nnaammee By default, only the user id is used when delivering email messages. Using this check box, the user name can also be used. Spaces are replaced by dots. For a user account "jack" with full name "Jacques Gelinas", email may be sent to either jack@the_domain or jacques.gelinas@the_domain. While this sounds appealing, it is not a recommend option. It is possible within your organisation to have two persons named identically. Unless you rename the first account, the older user will receive messages intended for the new user. The proper solution is to use only the account name, which is unique, so correspondents can't blindly guess the proper email address. 22..22.. EEnnaabbllee rreellaayy ccoonnttrrooll ((ssppaammmmeerrss)) Relay control lets you decide who may use your SMTP server (sendmail) to relay messages. Spammers are often borrowing SMTP servers to mass- distribute a message to a huge list of people. By enabling relay control, you can stop this from happening. Unfortunately, misconfiguring relay control rules may mean that some of your users won't be able to send email. This check-box allows you to enable/disable the rules. A new sendmail.cf file is generated, without losing the rules configuration. Note that this check-box DOES NOT control the "rejected senders" feature. "Rejected senders" allows you to reject email from well- known spammers. It does not limit the ability to relay. 22..33.. BBlloocckk ooppeenn rreellaayyss ((OORRDDBB)) It is a way to reduce spam. Check out http://www.ordb.org to learn about this feature. For every mail received, a special server is queried to accept or reject it. This service is free. Your server needs internet connectivity to use it. 22..44.. AAnnyyoonnee mmaayy rruunn mmaaiillqq Anyone may view the current state of the mail queue. 22..55.. AAnnyyoonnee mmaayy rruunn sseennddmmaaiill --qq Anyone may request sendmail to empty its queue. 33.. SSMMTTPP ffeeaattuurreess 33..11.. EEnnaabbllee tthhee VVEERRIIFFYY SSMMTTPP ccoommmmaanndd The VERIFY command allows the querying of an account to determine existence from the the mail transport protocol. In general, you do not want outsiders to probe your server like this. 33..22.. EEnnaabbllee tthhee EEXXPPNN SSMMTTPP ccoommmmaanndd The EXPN command expands an address. If the address corresponds to a mailing list, it will present all the members of the list. In general, you do not want outsiders to probe your server like this. 33..33.. EEnnaabbllee tthhee EETTRRNN SSMMTTPP ccoommmmaanndd The ETRN command lets anyone on the net request sendmail to run its queue for a specific domain. This is often used by mail servers with intermitent or on-demand connections. They send an "ETRN domain" request when they get online. 33..44.. EEnnaabbllee tthhee VVEERRBB SSMMTTPP ccoommmmaanndd 33..55.. RReettuurrnn ssuucccceessss DDNNSSss2211 This allows the "return receipt" messages. 33..66.. AAllllooww mmoosstt SSMMTTPP ssttaattuuss qquueerryy 44.. DDeelliivveerryy These options will let you control how mail is sent and received. 44..11.. MMeessssaaggee ssiizzee lliimmiitt You can restrict the maximum size of messages when they are received. 44..22.. DDoonn''tt ttrryy ttoo ddeelliivveerr iimmmmeeddiiaatteellyy This feature is intended for people without continuous Internet connectivity. This tells sendmail to save the mail without further checking. Later on, one can trigger the delivery of the messages. This is usually done by specifying a post connection command (see Linuxconf ppp dialout support) like "/usr/sbin/sendmail -q". This forces sendmail to process its queue and deliver the messages. In many cases, you may prefer to set the mail gateway protocol to expensive ESMTP, which queues outgoing mail, but processes local mail. 44..33.. PPrroocceessss qquueeuuee eevveerryy ((mmiinnuutteess)) This setting will instruct sendmail to process queued mail. Sendmail will wake up and try to deliver email that it was unable to deliver previously. You can see the content of the queue with the command "mailq" (without arguments). People without continuous Internet connectivity may want to play with this value. Setting the delay to 0 disables the feature. If your connectivity is _o_n_-_d_e_m_a_n_d, you may want to enter a larger number, such as 30 minutes. Then, when sendmail wakes up, it will/should trigger a connection to the Internet and process any queued mail. Those who disable this feature may want to control sendmail manually (or with a cron job) with the command: /usr/sbin/sendmail -q 44..44.. UUssee ssppeecciiaall sshheellll ssmmrrsshh Users are allowed to encode some processing instructions in their .forward file. The processing is done with the bourne shell (/bin/sh). Using this feature, processing is done within a "restricted" shell. This shell only executes commands found in the /etc/smrsh directory. 44..55.. MMaaxxiimmuumm rreecciippiieennttss ppeerr mmeessssaaggee A message may include several recipients and you may want to restrict the maximum number. 44..66.. SSeennddmmaaiill aanndd tthhee DDNNSS _S_e_n_d_m_a_i_l makes heavy use of the _D_N_S. Machines with no _I_n_t_e_r_n_e_t connectivity at all (even behind a firewall) may want to deactivate DNS usage. Alternately, machines with normal _D_N_S connectivity should force _D_N_S usage. 55.. MMiisscc.. 55..11.. NNoo bbaattcchhiinngg ffoorr uuuuccpp mmaaiill When relaying mail using UUCP, the messages are normally queued and delivered at a regular interval. You may want to deliver these messages immediately. If you have a low traffic load, this is often necessary. Email is forwarded immediately and users are happy. 55..22.. MMaaxx ssiizzee ffoorr uuuuccpp mmeessssaaggeess UUCP messages can be limited in size using this option. This is useful for slow modem links. Setting the maximum to 0 will disable this feature (no limit is set). Messages that exceed this value will be dropped. 55..33.. DDeelliivveerr llooccaallllyy ttoo uusseerrss Enter the name of users for whom you want to defeat the mail host definition. Messages will always be stored locally for these users. This feature is normally used for administrative pseudo users (root for one). 55..44.. NNoo mmaassqquueerraaddee ffrroomm uusseerrss You may want to defeat the "present your system as" field for some users. One such user is root. This easily allows the recipient to determine from which system (which root?) the message originated. 55..55.. TTrruusstteedd uusseerrss 55..66.. SSppeecciiaall rroouuttiinngg ddaattaabbaassee eennaabblleedd Check this if you intend to use special domain routing. Unfortunately, Linuxconf can't probe the sendmail distribution. You need to know if this sendmail supports a special routing database and which format is supported. These are "compile time" options for sendmail. No sendmail command line option will allow for the retrieval of those compile time features. 55..77.. SSppeecciiaall rroouuttiinngg ddaattaabbaassee ffoorrmmaatt _S_e_n_d_m_a_i_l may use several formats for parts of its database. It generally defaults to the dbm format. Please note that that some _s_e_n_d_m_a_i_ls only support one format (dbm). This is a compile time option. 55..88.. LLooccaall ddeelliivveerryy aaggeenntt Different utilities are used to manage email sent to local users. Those utilities provide various extensions allowing the user to tailor the delivery. Procmail, for one, supports fancy filtering. Some people use procmail to split incoming messages into several in-boxes based on various criteria. You can leave this field empty and Linuxconf will locate the proper utility available on your system. 55..99.. SSuuppppoorrttss bboogguuss mmaaiill cclliieenntt((HHEELLOO)) Some mail clients that use SMTP to send email are broken. They generate bad HELO sequences. Sendmail normally rejects such connections. With this option, sendmail is tolerant. It still accepts valid connections. 66.. AAlliiaasseess ffoorr yyoouurr ssyysstteemm Email messages which match the fully qualified name of your machine will be accepted by _S_e_n_d_m_a_i_l. Others will be either bounced back or forwarded. You may want to accept email messages for different domains. One situation is when you register with an Internet provider and he gives you one sub-domain of his own. You start using it, and later, you request your own domain. You still want to accept the old one, because many people know you by this address. You are allowed to enter as many lines as you need here. Use the Add button to grow the dialog.