Введите IP-адрес или хост сервера и нажмите проверить
Тест smtp-сервера заниманиет некоторое время (1-2 мин).

Более 10 тестов

Проверка SMTP-сервера по 10 важнейщим пунктам, проверка работы почтового сервера

Обратные записи

Проверка обратных записей rDNS (ptr) IP-адреса hostname почтового сервера

Тест на Open relay

Проверка безопасности smtp-сервера различными проверками на open relay

Проверка шифрования

Наличие поддержки защищеного соединения и шифрования трафика smtp сервера

Диалоги SMTP

Список всех диалогов между сервервами, скорость соединения и транзации


Инструкции по решению выявленных при проверке проблем smtp-сервера

Быстро и точно

Проверка сервера сразу по нескольким пунктам и точные результаты


Удобный и быстрый API для проверки IP-адреса или домена на DNSBL списки

How to check SMTP server?

Mail server, smtp server - in the e-mail forwarding system, the so-called agent of delivery/receipt of email messages. It is a computer program that transmits messages from one computer to another. Usually the mail server works "behind the scenes", and users deal with the program-the client of e-mail

When administering an smtp server, various errors often occur that worsen or completely block the delivery of letters. The most common problem is the incorrect configuration of the mail server, as well as the presence in blacklists (check for blacklists here). Let"s focus on errors, conditionally they can be divided into 2 categories: 1. Delivery errors, 2. Security errors.

The first category of errors associated with the delivery of letters can be attributed:

  • Invalid hostname
  • Missing required DNS records
  • Reverse host (rDNS) on the IP address does not match the server host.
  • Big connection timeout or transaction time.
  • Incorrectly configured firewall
  • Incorrectly configured server port
  • Hoster blocks port 25
  • Other errors

All of the above errors will not allow you to properly send a letter. Their decision can be key. Our free online diagnostic tool for smtp-server will be help to identify most problems. Checking the smtp server for 10 indicators: test for open-relay, available SSL / TLS, hostname, helo / ehlo, transit time and more. Yes, it is free and without registration.

How they manifest themselves, for example, errors with blocking port 25 or a large timeout will not allow you to send an email at all, even to establish a connection to the server.And errors with rNDS, hostname, DNS will provoke a complete and temporary disconnection of messages by the recipient’s server or by placing the message in the spam folder.

If the message is rejected by the recipient server with codes 500+ and 400+, you can say for sure that you should pay attention to rNDS, hostname and DNS, spam, etc. Typically, recipient servers provide additional information about the reasons for rejection.

For example, consider the popular errors that they mean

  • The server is blocked for spamming, blacklisting, missing DKIM and SPF rules. There may also be incorrect DNS record settings, invalid HELO / EHLO, the outgoing server does not support SSL connections. Comprehensive spam checking is also possible through our online tool spam test
    • 500x We do not accept mail from dynamic IPs
    • 500x Access from ip address blocked
    • 500x spam message discarded/rejected
    • 500x Spam message rejected
    • 500x Message rejected under suspicion of SPAM
    • 500x Message rejected as spam by Content Filtering
    • 500x Sorry, message looks like SPAM to me
    • 500x SPF check failed
  • Errors on the side of the recipient, the user does not exist, the recipient"s box is full. You can check email for existence and overcrowding through free email validator
    • 500x message sending for this account is disabled
    • 500x User not found
    • 500x No such user
    • 400x Mailbox Full
    • 400x Space shortage, please try later: retry timeout exceeded

Yes, there is a lot of information, the work of mail on the server consists of numerous technical subtleties. We continue on the second group of errors; I recall this security and encryption. It’s simpler here, each mail server should allow sending only to authorized users, i.e. Do not be open-relay and maintain a secure SSL / TLS connection. Open-relay (open relay) is extremely bad and means that anyone, without your knowledge, can send letters through your smtp-server, at least delivery degradation, and maximize server blocking by the host or mail services. Our tool also does an open-relay test.

We tried to briefly talk about common errors on the smtp server, however, we didn’t tell much. often the recipient servers return completely incomprehensible errors or do not behave at all predictably, all at the discretion of the system administrator serving the recipient"s mail server. You can check your mail server (smtp server) using our free tool, just enter the server address / host in the field at the beginning of the site.

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