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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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SMTP Connector for SBS 2008 (1and1 and rogers are not working)

I need an SMTP connector for my SBS 2008 server. The Domain/DNS is registered with 1and1 but due to recent issues they are being blocked by a lot of servers now. 1and1 also does not give me enough control over my DNS to allow me to setup the proper…
cpgascho
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Prevent SPAM by limiting SMTP connections using iptables

We operate a private VPN service which has been recently abused by spammers and we would like to be able to limit the number of SMTP connections per minute/hour to make it ineffective for spammers whilst still functional for normal use. I did my…
Michelle
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Exchange 2010 periodically stops responding to SMTP events with error 421 4.4.1 Connection timed out

After some help diagnosing why Exchange 2010 Enterprise stops responding to SMTP events. I can't find a pattern to it. It doesn't appear to be an actual timeout, as the server responds immediately with the error. To reproduce it I telnet into the…
Michael Shimmins
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How to safely send newsletters on VPS (SMTP) w/ non-hosted domain as "From" email?

Greetings, I'm trying to understand the safest way to use SMTP. I'm considering purchasing a second virtual server mainly for email sending, on which I will set up PHPlist (a free open-source mailing program), so we have the freedom to send…
Andy M
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Something is spamming from my hMail server - how can I deal with this?

My Windows 2008 server is attempting to send out a lot of spam, I've just discovered, and I'm not sure how to see where the compromise is. For example: has someone hacked an account? Has someone hacked the server? Is there a virus on the…
joshcomley
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SMTP 25 blocked externally

Not sure how to title this question... We run an Exchange server with around 80 internal users. All outgoing mail is relayed through a smart host (ISP SMTP server), so nothing is actually sent to the world directly from our server. I wanted to…
Jeff
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Can powershell be used to install SMTP service for IIS 6 and configure the options

I want to install the SMTP service for IIS 6 on windows server 2003. The GUI process is explained here on technet. Then I want to configure the properties (e.g. first retry interval) and create new domains etc. Can I script this using powershell…
softveda
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Paid SMTP service to decrease probablity being detected as spam?

Is it worth using paid SMTP service to decrease probability being detected as spam? What paid smtp services (except smtp.com) you know? PS: Of course, I'm not going to send spam. PPS: Probably this question is not for sysadmins & developers, but I…
Kirzilla
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Postfix: Relay access denied

When I telnet to my server thats running postfix and try to send an email: MAIL FROM: #=> 250 2.1.0 Ok RCPT TO: #=> 554 5.7.1 : Relay access denied I couldn't really find the answer on the site or…
JP Silvashy
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SMTP Deferred because of Reverse Lookup Errors

When sending emails I get about 5 out of 3000 emails that are status deferred because the PTR look failed according to the SMTP response of the receiving server. My PTR records are in order and match my EHLO. Can anyone else who sends a good amount…
Kyle Brandt
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exim4 issue with MX records

I have a Debian machine running Exim4. However, when checking the Exim log, I noticed this issue when mailing my own domain: 2010-12-14 09:20:01 1PSQ77-0005mG-9w ** root@domain.com: all relevant MX records point to non-existent hosts 2010-12-14…
Tuinslak
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PHP's SMTP configuration on ubuntu?

http://ca3.php.net/manual/en/mail.configuration.php#ini.smtp Looking at the manual, it specifies that the php.ini option for selecting an SMTP server is a windows-only thing. What do I do to configure it to use a specific domain/IP/port for a linux…
Incognito
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Anti-spam on par with Gmail's?

Currently, I rely on Gmail to weed out SPAM because the anti-spam software on my hoster's mail server is so crappy, and besides, it doesn't provide a good web UI so users can tag false negatives and improve its recognition rate. But I don't like to…
user15318
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SMTP not sending email in one server, but sends in another server

I have a section of code that sends email from SMTP server. The code is carried out webservice & smtp server value is picked up from web.config, while the code hosted on server1 works (send/receive emails), whereas the same code hosted in server2…
Sharpeye500
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New server cannot send mail

I'm retiring our 10 year old web server (no more Pentium III - yay!). A few of the pages on the web site it hosted have forms that cause e-mails to be sent to certain people. These e-mails are sent via the smtp server in IIS. We also use this…
Joel Coel
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