Run the tool from the command line by typing telnet in Command Prompt. (Note: Type cmd in the Start Search box to start Command. Prompt) Type open smtp.office365.com 587(25). If you connected successfully to an Office 365 server, you will receive a response line similar to below.
![Telnet Telnet](/uploads/1/2/5/3/125385754/631490059.png)
Telnet Commands SMTP Check Port 25Telnet port 25 / Telnet SMTP commandsSMTPcheck port 25 with the Telnet commandYoucan check your SMTP Server on SMTP port 25 with the following Telnetcommands:Open a command line and typetelnetsmtp-server.domain.com 25You can also dothis with PuTTY.
To make sure you understand all the details of what we are about to discuss, let’s define what SMTP is and what can be tested with it.SMTP (Simple Mail Transfer Protocol) is the methodology behind the email workflow on the Internet. People have probably been wondering how emails get to their destination. SMPT fully covers it, implementing something similar to the mechanism of delivering an actual letter in an envelope. The SMTP server, or just a computer running SMPT, stands for a mail carrier of the Internet. The messages are sent directly to this server, which consequently delivers mails to their receivers. Quite convenient, isn’t it?Various things can be tested with simply telneting into a given SMPT server:. is server working?.
is it a firewall that blocks communication?. does the mail server allow for relaying of a particular domain or an email address?. what SMTP commands does the mail server support?. how much time does it take for a server to response?. does the server respond with the correct hostname?How to test SMTP server with a manual telnet session?First, a telnet client has to be verified for the installation on the server.
Then, you should search a mail server to log in to. We will need the DNS MX record for a given domain to proceed it. You can use something similar to the following command:Windows: nslookup -type=mx mailtrap.ioLinux: nslookup -type=mx mailtrap.ioNon-authoritative answer:Server: 192.168.0.1Address:192.168.0.1#53Non-authoritative answer:mailtrap.iomail exchanger = 10 aspmx2.googlemail.com.mailtrap.iomail exchanger = 10 aspmx3.googlemail.com.mailtrap.iomail exchanger = 1 aspmx.l.google.com.mailtrap.iomail exchanger = 5 alt1.aspmx.l.google.com.mailtrap.iomail exchanger = 5 alt2.aspmx.l.google.com.For the IP we are going to use, we need the DNS PTR.
For this, we should start with the IP address the Internet sees us as having. Sites like this can be a perfect solution in this case.Once you figured out your IP address, run the following command, with T.T.T.T standing for the IP address.Windows: nslookup -type=ptr T.T.T.TLinux: nslookup -type=ptr A.B.C.DServer: 192.168.0.1Address:192.168.0.1#53Non-authoritative answer:212.235.118.46.in-addr.arpaname = SOL-FTTB.212.235.118.46.sovam.net.ua.We now have two basic requirements – the MX record for railsware.com and the PTR for the IP we will use. At this point, you can log in to the SMTP server.