Configuring the outgoing mail server agava net. DNS. Principles of work, basic records. Payment methods for services

DNS (Domain Name System) is a system that allows you to convert symbolic domain names to IP addresses (and vice versa).

Domain - a specific zone in the Internet domain name system (DNS), allocated to a country, organization or for other purposes.

How DNS works

The domain name system has a hierarchical structure using an arbitrary number of constituent parts (domain), separated from each other by a dot ( . ). On the Internet, the root domain or domain top level operated by InterNIC. A system of two-letter top-level domains has been created for each country (about 300):
-USA, -Canada, -Germany, -Russia, -the former USSR, -France, -Finland, -Italy, -Switzerland, -United Kingdom.
And also for different types organizations:
-profit organizations;
EDU-educational establishments;
GOV- government agencies;
MIL-military institutions;
-other organizations;
-network resources.

In Russia, the "Domain RU Coordination Center" is responsible for domain.RU.

To determine the IP address by the domain name, the DNS service is used, which consists of many DNS servers containing a distributed database of mappings " domain name - IP address. "Each network must have at least one DNS server that maintains a local database of domain names and searches for an IP address by domain name.
This search is done as follows:

• a query is made to the local DNS server;
• if the DNS server knows the answer, it returns it to the client (the corresponding record is in its table or in the cache);
• if the DNS server does not know the answer, it refers to the next DNS server by reference until the corresponding record is found (recursive scheme).

Hostname and IP address are not the same - a host with the same IP address can have many names, which allows you to support many websites on one computer (this is called shared hosting). The opposite is also true - one name can be associated with multiple IP addresses.

Reverse DNS lookup

DNS is primarily used to translate symbolic names to IP addresses, but it can also perform the reverse process. For this, existing DNS tools are used. The fact is that various data can be associated with a DNS record, including a symbolic name. There is a special domain in-addr.arpa, which records are used to convert IP addresses to symbolic names. For example, to get the DNS name for the 11.22.33.44 address, you can query the DNS server for the 44.33.22.11.in-addr.arpa record, and it will return the corresponding symbolic name. The reverse order of writing the parts of an IP address is explained by the fact that in IP addresses the most significant bits are located at the beginning, and in symbolic DNS names, the most significant (closer to the root) parts are located at the end.

DNS records

Let's consider in detail the DNS records, what they are for:

SOA record(start of authority record) indicates on which server the reference information for this domain is stored:

Start Of Authority
example.org. 86400 IN SOA ns1.agava.net.ru. noc.agava.com. (
2006092102; Serial
10800; Refresh
1800; Retry
3,600,000; Expire
86400); Minimum TTL

This record is created when creating a zone for a domain. If this record does not exist, the registrar receives error messages of the form:

From the DNS server ns2.agava.net.ru. (89.108.64.2), it is not possible to get the SOA record for the EXAMPLE.ORG domain.

The name field can contain the @ symbol to indicate the name of the current zone. In this example, you could have used @ instead of example.org.

There is no time field. The class is IN (Internet), the type is SOA, and the rest of the elements make up the data field.

The ns1.agava.net.ru server is the main name server for this zone.

The noc.agava.com entry specifies the email address for technical contacts in the format user.machine, (not user @ machine).

Serial - Serial number. The serial number of the zone file. It should grow every time you make changes to the domain data. When the secondary server wants to check if the data needs to be updated, it checks the SOA record serial number on the primary server.

Refresh - Update. The time in seconds that determines the frequency of checks by the secondary server serial number on the primary and starting a new exchange, if there is new data on the primary.

Retry - Repeat. When the secondary server cannot connect to the primary, after the update time has elapsed (for example, if the host is down), this value defines the delay in seconds between retrying updates.

Expire - Deadline. If repeated attempts to update are not successful within this time, the secondary server destroys its copy of the zone file (s) data and stops responding to requests for that domain. This stops the repetition and circulation of very old and potentially inaccurate data.

TTL - Lifetime. This field specifies the time, in seconds, that a resource record for this zone remains valid in the cache of other servers. If the data changes, this value should be small. TTL is a commonly used abbreviation for Time To Live.

NS record(name server) points to the DNS server for this domain.

NameServers
example.org IN NS ns2.agava.net.ru
example.org IN NS ns1.agava.net.ru

Also, for domains below the second level, we can add DNS to partner servers, for example:

love.example.org IN NS ns2.loveplanet.ru
love.example.org IN NS ns1.loveplanet.ru

This will work provided that a zone for these domains will be created on the loveplanet.ru servers.

MX record(mail exchange) or mail exchanger specifies the mail exchange server for this domain.

Mail eXchangers
example.org IN MX 10 cluster.relay.agava.net
example.org IN MX 20 mail.example.org

The number before "cluster.relay.agava.net" is the priority value, lower number means higher priority. MX records are used by the email system to route mail more efficiently. MX records are used to send mail messages not directly to the addressee, but to mail server at the recipient's site.

In the above example, mail will arrive at the cluster.relay.agava.net server first (priority 10

Record A(address record) - an address record associates a host with an IP address.

INternet Addresses
example.org IN A 192.0.2.77
This entry can be viewed with the host command (for * NIX systems):
$ host example.org
example.org has address 192.0.2.77

The main purpose of the address record is to establish a correspondence between the domain name of the machine and the IP address. Actually, this is the main task of the entire domain name system. For this reason, the address resource description record is one of the key zone description records.

Here we will touch on the question of how to change the MX record for your domain. To do this, you need to write to us an application from the contact e-mail "a (for individuals) or send a scan of the application letter in free form on the company's letterhead with the seal and signature of the head or responsible person (for legal entities) with a request to change / add MX record, specify the IP or name of the new mail server.

CNAME record(canonical name record) or canonical name record is used to redirect to another name.

CNAME stands for the canonical name or synonym for an existing hostname, which must have an A record. Example:

love.example.org IN CNAME loveplanet.ru

SPF (Sender Policy Framework) records that prevent spammers from sending emails on behalf of domains that do not belong to them.

SPF allows the domain owner to specify a specially formed string in the TXT record of the DNS server that specifies the list of servers that can send email messages on behalf of this domain.

Mail transfer agents receiving mail messages can request SPF information using a simple DNS query, thus verifying the sender's server.

An example of SPF data in a TXT DNS record:

example.org. IN TXT "v \u003d spf1 a mx -all"

v \u003d Specifies the SPF version to use. The following is a list of verification mechanisms: in this case, "a" and "mx" allow sending letters for all A and MX records of the example.org domain. The line ends with "-all", indicating that messages that have not been verified using the above mechanisms should be ignored.

PTR record (Pointer) - "reverse zone" pointer entry.

The task of finding a domain name by IP address is the reverse of the direct task - finding an IP address by a domain name. As mentioned above, the direct problem is solved in DNS using A (Address) records. The inverse problem is solved using pointer records of the PTR (Pointer) type, which, together with SOA and NS records, form a description of the so-called "reverse" zone.

The "inverse" problem is solved by a special domain, the structure of which coincides with the structure of IP addresses. This domain is called IN-ADDR.ARPA. We will not go into the intricacies of his work here, you can read about this in detail at:
We only note that We do not register PTR records, due to the impossibility of this operation on shared hosting.

SRV records (Server selection) an indication of the location of servers for certain services, for example, Jabber, Active Directory.

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Fighting spam at the user level is the last line of defense. A lot of tools are being developed for this milestone. Agava recently released a spam filter for the private user Agava Spamprotexx. This program is not trial versioncreated by a group of enthusiasts. This software product was developed by professionals working directly at Agava. Agava has over 6 years of experience in software development and employs over 100 experienced employees. Company projects in russian Internet are in the top five in terms of attendance.

Agava Spamprotexx works on the basis of statistical methods

Some programs of a similar class, for example SpamFilter from DeSofto, delete messages on the server of those messages that the program qualifies as spam with a certain level of probability. Agava Spamprotexx does not do this: the mail is downloaded completely. Messages classified as spam are stored in a specific folder, from where the user himself deletes them. This measure ensures that false positives (normal emailclassified as spam) of the program's work. The program does not care what protocol the user receives mail: POP or IMAP, while the program does not even need to specify a specific type of mail protocol.

Agava Spamprotexx works with all email clients and does not require their configuration, while most of the common filters work as proxy servers: they take mail to themselves and then give it to the client. That is, the client applies for mail to the proxy, which requires changing the settings. In itself, changing the settings does not present much difficulty in similar programs, but for an unskilled user it can present certain difficulties. The Agava Spamprotexx user is spared this hassle.

If necessary, you can disable the spam filter from work in one click and work with mail without it. The need for such a shutdown during the program testing period arose once: when sending mail failed. When contacting the developers, it turned out that the error had already been fixed and an update was needed. Agava Spamprotexx provides the function automatic update, but manual, on demand, no. In such cases, you have to download the updated version manually, using some download manager, and then install new version on top.

Program settings

The basic principle of settings is a minimum of hassle for the user

The program settings are very simple and are divided into groups of parameters.

Are common - basic parameters of program settings. In this window, you need to enter the mail addresses for letters intended for training the program, a label for indexing spam messages, define a folder for placing filtered letters (if the user is not satisfied with the folder, created by the program default). In the same window, you can enable / disable the integration of Agava Spamprotexx into Microsoft mail clients: Outlook Express and Microsoft Outlook.

In these mail clients To train Agava Spamprotexx on incoming spam, simply drag & drop the letter into the corresponding baskets built into the command panel of the email client. In the mail clients of other developers, you have to perform a few simple steps to learn. It's less convenient than Outlook, but still not difficult.

Friends - "white" list of verified correspondents. Letters from correspondents from the "white" list are not scanned by the program at all. The "white" list consists of postal addresses and their corresponding text names. It often happens that spam comes from well-known addresses - this is called e-mail forgery. At the same time, spammers rarely forge the corresponding text name along with the address. Therefore, the whitelisting in Agava Spamprotexx is more reliable than in other programs.

The "white" list is supported automatically. If you send a letter to someone, their address and text name are added to the "white" list. If you submit a non-spam message for training, its address and text name will also be added to the whitelist. If you provide the filter with a spam message for training, its address will be removed from the "white" list. In order for an address from the "white" list to be protected from deletion, you must manually check the box for confirmation of deletion opposite a specific address. The whitelist can also be maintained manually.

Ports - the ability to configure certain ports to work under certain protocols, if they differ from those used by default.

Algorithm - the ability to manage the coefficient, which serves as a threshold for classifying a message as spam. The default filtering value of 60% is the company recommended threshold. But the user can either lower the value of this threshold, or raise it. If you want to get as few false positives as possible, place the spam cutoff in this Spamprotexx tab by 80 or even 90%. In this case, the user will have to send more sample spam messages for training, but the number of non-spam messages mistakenly marked as spam will decrease.

Statistics - analysis of the program. None of the existing spam filters can guarantee 100% spam protection. First of all, because the technologies of spam mailings are constantly changing and improving. But the user must follow the effectiveness of the program, otherwise how can he evaluate the effectiveness of the program and, ultimately, the effectiveness of his invested funds.

Program operation

Agava Spamprotexx does not slow down the reception and sending of mail at all. By integrating into the process of receiving mail at a low level, the spam filter checks incoming and outgoing mail. With the help of the training function, the user sets up filters for his individual characteristics of correspondence. All messages marked with the "Spam" tag go to a specific folder, which the user can view as needed. The developers claim that Agava Spamprotexx can save up to 20 minutes of user time for every hundred spam messages. This is not counting the nerves.

To learn the program, you need to send a message to a specific address

Learning, as already mentioned, is carried out by sending messages passed through the filter to certain addresses (the algorithm of this operation is described in detail in the User's Guide) or by transferring these messages to the appropriate baskets. In the process of learning, the transfer or transfer operation has to be performed less and less often.

In general, we can say with confidence that Agava Spamprotexx classifies letters quite confidently. It can make life and work much easier for those users whose e-mail addresses are freely available on websites, forums, and so on.

The exclusive rights to publish and distribute the program on the territory of Russia, the CIS countries and the Baltic States belong to CJSC "New Disc". You can get acquainted with the spam filter by downloading the distribution kit from the Agava website. You can buy Agava Spamprotexx in a DVD-box at Softkey or through the Novy Disk company online store.

System requirements:

• operating room microsoft system Windows 98SE / ME / NT / 2000 / XP;
• pentium processor 100 MHz;
• 32 MB random access memory;
• Internet Explorer 4.0;
• screen resolution 800x600 with 16 bit color depth.

Inexpensive hosting will be a good start for beginners and is suitable for creating static HTML sites. If your project grows into a commercial resource, you can always choose a more powerful hosting plan with PHP and MySQL support for large, high-load sites and professional platforms. For legal entities (including LLC), electronic document management (EDM) is available, which allows you to quickly exchange documents and perform operations with hosting and domain services.

Specifications hosting includes high-performance SSD RAID, Linux CentOS or Windows for ASP.NET with Python, Java, PHP, Perl and Django framework support (starting from Host-A). The ftp server is accessed via FTP and SSH protocols.

The security of your site is important to us, therefore, in addition to the hosting service, you will receive for free:

• protection against DDoS attacks;
• unlimited traffic;
• double anti-virus check;
• SSL certificate.

For better site security, you can additionally order the treatment of infected files and extended protection against spam.

When transferring hosting to REG.RU for any tariff, you will get a month of free service!