{"id":3679,"date":"2019-11-28T01:37:24","date_gmt":"2019-11-27T23:37:24","guid":{"rendered":"https:\/\/www.msb365.blog\/?p=3679"},"modified":"2023-06-23T13:05:16","modified_gmt":"2023-06-23T11:05:16","slug":"telnet-email","status":"publish","type":"post","link":"https:\/\/www.msb365.blog\/?p=3679","title":{"rendered":"Use Telnet for sending e-mails"},"content":{"rendered":"

Prolog<\/h3>\n

This article is about an old school topic. In the last few weeks after my vacation, I was supporting a company who had issues between a server and the mail environment to send emails.<\/p>\n

In this company, the messaging environment is configured that only authenticated systems are allowed to send messages. This I have configured threw a Kemp Load-balanced.<\/p>\n

\u00a0<\/p>\n

However, in the particular case one system was not able to send messages, from the messaging site the configuration was right. I recommended the service owner to try to send a mail using Telnet.<\/p>\n

It seems that Telnet is an old school method for testing and troubleshooting. The service owner did not know how to send mails using Telnet.<\/p>\n

Of course that is not bad, for this reason I will explain in this article how to use Telnet to send messages.<\/p>\n

\u00a0<\/p>\n

On-premise<\/h3>\n

To use Telnet on an on-premise environment we need to start the command prompt on the system we want to test the connection.
\nIn the command prompt we type the command Telnet<\/strong> with the IP of the Exchange server and the Port you want to connect. By default the Port is 25, but in our example we are using the Port 587:<\/p>\n

telnet 10.54.69.32 587<\/pre>\n
\"\"<\/p>\n
\u00a0<\/p>\n
If Telnet is allowed on the right Port, we will be connected to the remote server, the answer we get can look like in the picture below:<\/p>\n
\"\"<\/p>\n
Note: From now we are not allowed to make any typo mistakes. Otherwise we will need to start over again from the beginning.<\/p>\n
The remote Exchange Server is now ready to receive orders from us. We start with saying hello to the server:<\/p>\n
helo a<\/pre>\n
\u00a0<\/p>\n
Now we should receive a 2XX message from the remote Exchange, that shows us that we are allowed to communicate.<\/p>\n
\"\"<\/p>\n
In the next step we need to enter a sender address. This can be performed with the command:<\/p>\n
Mail from:alias@contoso.com<\/pre>\n
\"\"<\/p>\n
\u00a0<\/p>\n
Now we need to enter the recipient, the command for that is:<\/p>\n
rcpt to:alias@fabrikam.net<\/pre>\n
\"\"<\/p>\n
\u00a0<\/p>\n
The main things are now set, now we continue with the mail data. For that we run as first the command:<\/p>\n
Data<\/pre>\n
\"\"<\/p>\n
\u00a0<\/p>\n
Now we need the Message subject, this can be enterd with the command:<\/p>\n
Subject:Testmail for documentation<\/pre>\n
\"\"<\/p>\n
\u00a0<\/p>\n
In the next line we can now start writing the mail text we want to send. After we entered the subject and hit enter, we can start entering a text for the recipient.
\nTo finish the mail, we hit enter again and then a point \u201c.\u201d To tell the remote server that the mail is finished.<\/p>\n
\"\"<\/p>\n
In the end we only need to close the telnet session by entering quit<\/strong> and everything is done.<\/p>\n
\"\"<\/p>\n
A few moment later I have received the email we just have sent threw telnet.<\/p>\n
\"\"<\/p>\n
\u00a0<\/p>\n
With this test I was able to prove the service owner, that from the messaging site everything is working fine. So he had to find the issue on an other place.<\/p>\n
\u00a0<\/p>\n
Exchange Online<\/h3>\n
If we are using Exchang online, we are also able to create a telnet session. To do that we can follow the similar steps. First of all, we need to get a connection to our Exchange online tenant using telnet. In this example I will use the Exchange online from the MSB365 Tenant:<\/p>\n
We need to open a command prompt and type the Telnet command using the syntax bellow:<\/p>\n
Telnet yourtenant-com.mail.protection.outlook.com 25<\/pre>\n
\"\"<\/p>\n
\u00a0<\/p>\n
In the following screenshot, we can see the result, the answer from the EOP server appears on the screen:<\/p>\n
\"\"<\/p>\n
\u00a0<\/p>\n
From this point we can use the same commands to send emails like we saw in the previous chapter.<\/p>\n
\u00a0<\/p>\n
Conclusion<\/h3>\n
First of all note: Telnet is only working if the security is set to allow this type of connection. If you are not able to connect a server by using Telnet the reason can be that the IP is wrong or Telnet is not permitted.<\/p>\n
\u00a0<\/p>\n
\u00a0<\/p>\n
\u00a0<\/p>\n
\u00a0<\/p>\n
Photo by\u00a0Ben White<\/a>\u00a0on\u00a0Unsplash<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
Prolog This article is about an old school topic. In the last few weeks after my vacation, I was supporting a company who had issues between a server and the mail environment to send emails. In this company, the messaging environment is configured that only authenticated systems are allowed to send messages. This I have […]<\/p>\n","protected":false},"author":1,"featured_media":3686,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"footnotes":""},"categories":[1923,2],"tags":[],"class_list":["post-3679","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-microsoft-365","category-exchange"],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.msb365.blog\/index.php?rest_route=\/wp\/v2\/posts\/3679","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.msb365.blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.msb365.blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.msb365.blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.msb365.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3679"}],"version-history":[{"count":6,"href":"https:\/\/www.msb365.blog\/index.php?rest_route=\/wp\/v2\/posts\/3679\/revisions"}],"predecessor-version":[{"id":5182,"href":"https:\/\/www.msb365.blog\/index.php?rest_route=\/wp\/v2\/posts\/3679\/revisions\/5182"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.msb365.blog\/index.php?rest_route=\/wp\/v2\/media\/3686"}],"wp:attachment":[{"href":"https:\/\/www.msb365.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3679"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.msb365.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3679"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.msb365.blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3679"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}