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Questions tagged [smtp]

SMTP is the Simple Mail Transfer Protocol, the most recent standard of which is defined in RFC 5321. It's the Internet standard for sending and receiving email.

Some characteristics of SMTP (Simple Mail Transfer Protocol):

  • The default port is TCP port 25 and new submissions (MSA) is port 587.
  • Although depreciated, some services still use port 465 (SMTPS) to support legacy applications.
  • It is used to transmit outbound mail, and mail servers (which listens on port 25) receives mail on port 25.
  • It should not be confused with POP3 / IMAP which is an actual store for the e-mail. SMTP messages are received by the receiving server and then an MTA moves it to the POP3 / IMAP mailbox where it is normally retrieved using a POP3 / IMAP client.

See Also:

RFC5321

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How to determine which scripts are sending mail via Default SMTP Virtual Server

I run a small server hosting sites for around 100 unique clients. I've had issues with my legitimate mail server showing up on DNS Blacklists, so I need to find out if one of my many clients has a bad script somewhere sending junk through my SMTP…
Dan Short
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Exchange 2010 unable to send to external email address using a receive connecter

I have set up receive connector on my Exchange 2010 server to receive email from my Nagios box. I have an external email address in my contacts for nagios to convert emails to text. It seems exchange is refusing to relay mail to an external address…
user89350
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Setting MX records to allow different servers to send and receive email

I have a site (mydomain.com) that uses the hosting service to send and receive emails (the MX points to mail.mydomain.com). Now I want to keep the same server to send emails but use a third party service to receive and process the incoming emails…
willvv
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Help with SMTP troubleshooting

my friend ask me to help because he cannot send email from his company. i just have little knowledge about mail server so what i do: dig mx hiscompany.name then try to send using telnet with port 25 no answer. telnet mx.hiscompany.name 25 then try…
uncle don
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How Do I Troubleshoot Exim Mail Retry Issues?

My server is encountering high CPU load (like almost pegged at 100%) so much that the Apache service can't run and we get Apache 500 errors. We used a script to catch this and this is where we discovered that normally the server doesn't run a bunch…
ServerChecker
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Packet sniffing SMTP connection

I have a program on Windows that sends email via a remote SMTP server, and it is failing with an ambiguous "cannot connect" error message with no log or other information as to why it is failing. I have tested the SMTP server and confirmed it is…
jrdioko
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Windows 7 outgoing port blocked

I am in charge of a small company's IT department, and am well versed in UNIX/Linux (which our server runs) but not so well versed in Windows (which many of our employees run). We have a website and a mail server hosted at…
fmt
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Block certain images from incoming emails

My company just added 5 of the social networking images to its email signature. Now we have tons of copies of these identical images stored in the software that takes emails and turns them into tickets of some kind (Jira does this, but this isn't…
JoeB
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Preventing MX record fallback

I have a website, example.com, running on a Windows 2008 server with IIS 7 and the "IIS 6" SMTP service. The website regularly sends out emails to info@example.com. In rare instances, the MX record lookup for example.com fails, and so the SMTP…
anon
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SMTP Question. Why does send succeed when Authentication fails

I have an application written in .NET framework that sends emails using our STMP server. I was researching another emailing issue which caused me to look at the SMTP logs. Here is a sample SMPT log entry... 00:10:35 [64.77.200.185][43483994] rsp:…
Seth Spearman
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UNIX SMTP client that supports MS Exchange proprietary (EXPS) authentication?

I'm trying to non-interactively send emails from Solaris through an Exchange 2007 server, but the Exchange server only allows Exchange Server authentication (OWA access is also disabled). Here's the list of enabled authentication methods returned…
MisterEd
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What Linux mail server is easiest to setup?

I need to send emails from web application using Gmail accounts. As far as I understand, sending them directly will freeze worker process for quite a long time (it's a Rails app running on Apache/Passenger). So I want to install local SMTP server…
synapse
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PHP Warning: mail(): SMTP server response: 501 Must specify to address <address>

Cannot understand why I am getting this error - both to & from email addresses are valid (I use them daily) so cannot figure out how this is happening - any help would be appreciated. NOTE: This is working in production but is throwing errors in…
php-b-grader
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VPS - The easiest way to start sending email

I have installed (clean) Debian 6 on VPS, and I am running a Django-powered application on it. Everything works fine, except that I need to set up SMTP to enable my application (meaning sender is local) to send out emails to its users (so, the…
Mladen Jablanović
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SMTP smarthost round-robin balancing

Our SMTP provider requires to distribute emails evenly between four different hosts. I understand that the standard way to distribute this kind of load is utilizing DNS round robin feature, but the problem is that provider's mailservers should be…
Alex
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