Shulou(Shulou.com)06/03 Report--

Question1: what is Postfix and what is its default port?

A: Postfix is an open source MTA (mail transfer agent, English name: Mail Transfer Agent) that forwards email. I believe many people know Sendmail, and Postfix is its replacement. The default port is 25.

What is the difference between 2:Postfix and Sendmail?

A: Postfix uses a modular design and consists of multiple independent executable programs, while Sendmail is designed to have a powerful background process to provide all services.

Question 3: what is MTA and what role does it play in the mail system?

A: MTA is an abbreviation for Mail Transfer Agent (Mail transfer Agent). MTA is responsible for receiving and sending emails, determining the sending path and address rewriting. (LCTT: address rewriting, that is, perfecting the sending address, such as rewriting the address "username" to "username@example.com"). Local forwarding is the sending of messages to MDA. Qmail, Postix and Sendmail are all MTA.

Question 4: what is MDA?

A: MDA is an abbreviation for Mail Delivery Agent (Mail delivery Agent). MDA this program is used to get mail from MTA and deliver it to the mailbox of the local recipient. MDA can usually filter messages or classify messages. A MDA can also determine whether an email needs to be forwarded to another email address. Procmail is a MDA.

Question 5: what is MUA?

A: MUA is an abbreviation for Mail User Agent (Mail user Agent). MUA is an email client software that can be used to write, send and receive emails. When sending mail, you can use MTA; to receive mail directly from the mail storage area, or indirectly through the POP/IMAP server. Outlook, Thunkerbird and Evolution are all MUA.

Question 6: what is the role of postmaster in the mail server?

A: generally speaking, the email manager is postmaster. The responsibility of a postmaster is to ensure that the mail system is working properly, update the system configuration, add / delete mailbox accounts, and other work. There must be a postmaster alias in each domain. Postmaster aliases are used to receive messages from other servers / users about the mail system, such as complaints about spam rejection, which are usually directly accepted by the administrator of the mail server. Some emails with system errors and prompts, often with postmaster as the sender, are used to send messages to the right users.

Question: what are the important processes of 7:Postfix?

A: the following is a list of the most important background processes in the Postfix mail system:

Master: this process is the brain of the Postfix mail system, which generates all other processes.

Smtpd: handles all externally connected requests as a server-side program.

Smtp: handles all requests to initiate a connection as a client program.

Qmgr: it is the heart of the Postfix mail system, processing and controlling all messages in the mail queue.

Local: this is Postfix's own local delivery agent MDA, which is responsible for saving mail to the mailbox.

What is the configuration file for the problem 8:Postfix server?

A: there are two main configuration files:

/ etc/postfix/main.cf: this file holds global configuration information, which is used by all processes unless these configurations are reset in the master.cf file.

/ etc/postfix/master.cf: this file holds additional process runtime environment parameters, and the configuration defined in the main.cf file may be overwritten by the configuration in this file.

Q9: how to restart Postfix and set it to boot?

Answer: restart with this command: service postfix restart; use this command to boot: chkconfig postfix on

Question 10: how do I view Postfix's mail queue?

Answer: Postfix maintains two queues: the pending mail queue (pending mails queue) and the waiting mail queue (deferred mail queue). The waiting queue contains messages that have temporarily failed to be sent and need to be resent, and Postfix will resend them regularly (default is 5 minutes, which can be customized). (LCTT translation note: in fact, Postfix maintains five queues: input queues, messages enter the first station of the Postfix system; active queues, qmgr moves messages from input queues to active queues; waiting queues to save messages that cannot be sent temporarily; failure queues to save damaged or unreadable messages; and keeping queues to keep messages in the Postfix queuing system indefinitely. )

List all messages in the message queue:

# postqueue-p

Save the mail queue list:

# postqueue-p > / mnt/queue-backup.txt

Have Postfix process the queue immediately:

# postqueue-f

Question 11: how do I delete messages from the mail queue?

A: the following command deletes all messages:

# postsuper-d ALL

The following command deletes only messages in the waiting queue:

# postsuper-d ALL deferred

Question 12: how do I check Postfix configuration information through commands?

A: you can view it using the postconf-n command, which will filter out the commented-out configuration information in the configuration file.

Question 13: what command should I use to view the mail log in real time?

A:

Tail-f / var/log/maillog or tailf / var/log/maillog

Question 14: how do I send a test message from the command line?

A: refer to the following command:

# echo "Test mail from postfix" | mail-s "Plz ignore" info@something.com

Question 15: what is Open Mail forwarding (Open Relay)?

A: open mail forwarding is a setting of the SMTP server that allows any other user on the Internet to forward mail through the server, rather than sending it directly to an account's server or only allowing authorized users to send mail through it. In the past, this feature was enabled by default on many mail servers, but it is no longer popular because email forwarding can lead to a large number of spam and virus messages raging on the Internet.

Question 16: what is a mail forwarding host on Postfix?

A: the forwarding host is the address of SMTP. If it is configured in the configuration file, then all input messages will be forwarded by the SMTP server.

Question 17: what is a gray list?

A: the LCTT is a technology used to intercept spam. When a MTA uses a gray list, it "temporarily rejects" all messages sent by unidentified senders. If the email is justified, the initiator will resend it after a period of time, and then the email can be received. The gray list is based on the fact that most spam servers and botnets send messages only once, ignoring requests that require them to send again after a certain interval. )

Question 18: what is the important role of SPF records in the mail system?

A: SPF is an acronym for Sender Policy Framework and is used to help mail domain owners confirm whether the sender is from their domain. The purpose is that other mail systems can ensure that the sender comes from an authorized source when sending mail-this method reduces the risk of email address spoofing, phishing and spam.

Question 19: what is the use of DKIM in the mail system?

A: the domain key is an email authentication system used to verify the sender's DNS domain and the integrity of the message. Domain name key specification adopts Internet e-mail authentication technology and establishes a set of enhanced protocol: domain name key identification email (DKIM).

Question 20: what are the rules of ASSP in the mail system?

A: ASSP (Anti-Spam SMTP Proxy, anti-spam agent) is a gateway server installed in front of your MTA. Anti-spam is anti-spam through self-built whitelist, automatic learning Bayesian algorithm, gray list, DNS blacklist (DNSBL), DNS whitelist (DNSWL), URI blacklist (URIBL), SPF, SRS, Backscatter, virus scanning, attachment blocking, sender and other methods.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.