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:
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
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.