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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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Configuring SPF, DKIM, Reverse DNS for VPS sending email through Google Apps SMTP servers

Today we realized that all of our emails being sent to email addresses of the type @corporatedomain.com were getting rejected. I don't know who is hosting the email for corporatedomain.com. I don't think that should matter. Anyway, the…
Amith George
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Can't connect to smtp (postfix, dovecot) after making a change and trying to change it back

I am using postfix and dovecot along with zpanel and I tried enabling SSL and then turned it off as I did not have SSL configured yet and I realized it was a bit stupid at the time. I am using CentOS 6.4. I get the following error in the mail log.…
Uberswe
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Email verification with SMTP fails on local machine for certain domains

I want to verify whether mail box exists for a email with SMTP. I am able to do following things : Get MX records from domain Connect to host via SMTP Then I execute following commands : HELO somedomain.com MAIL FROM: …
vedarthk
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False positive rate of CBL

We've come into the office (30+ networked systems) this morning to find that our email server is blacklisted on the CBL for: This IP address is infected with, or is NATting for a machine infected with the ZeroAccess botnet, also known as Sirefef.…
Jamie Taylor
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Configure IIS SMTP server to forward to more than one address

I have the SMTP service installed on Server 2008 R2. Under Domains, if I go to properties, under Route Domain, I have the option to forward all mail to smart host and I currently have one address [nnn.nnn.nnn.nnn]. Is it possible to have more than…
Dave
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How to clean up Badmail directory?

I was inherited this server so I'm not yet fully familiar with its setup. However, I noticed that C:\inetpub\mailroot\Badmail\ directory contains ~400,000 files. For now I do not want to delete the whole thing, only perhaps files older than…
Mxx
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Can't connect mercury mail smtp server outside local network

I'm using Windows Server 2008 R2, and Xampp with mercury mail. My problem is that I can't send mails via my server outside the server network. My SMTP server is using port 25, which is open and accesible outside the local network. But telnet…
user163810
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What allows a mail server to operate faster or handle more mail?

I realize that this may be better suited for StackOverflow.com instead, however as I'm not much of a developer, I worry those answers may be way too developer-centric. Although, I would like some nitty-gritty details where possible and in a…
uzzi09
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ICS attachments disappear after migrating to exchange 2007

We currently have a small c# script that pulls a calendar appointment from Siebel OnDemand and mails it out to our users using smtp. This all worked before we migrated some users to Exchange 2007 this weekend. Now the .ics calendar file doesn't show…
jdiaz
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PHPMailer script stopped working with cryptic SMTP error messages

I am trying to send mail in a PHP script via the PHPMailer library. The following code has successfully sent emails in the past without warnings: function mail_attachment($filename, $path, $mailto, $subject, $message) { …
user143089
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How can I tell my server to allow logins via a mail client?

I am setting up my first sendmail daemon on centos, using virtual domains and emails. So far, I have got it working and emails sent from remote servers will make it to the inbox. The problem I have is actually logging in to the server with a mail…
willdanceforfun
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Any software/proxy that can do SMTP failover?

I'm using a monitoring software that sends out email to my ISP's mail server (SMTP Server). But sometimes, the ISP's mail server goes down, or takes too long to respond, I would like to find out if there's a Windows software/proxy that can forward…
Joshua Lim
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Postfix: don't bounce for remote rejects

I'm having a problem with sending bounces to spammers when a remote "trusted" smtp server rejects a mail. My server manages mail for company1.com that has a virtual alias support@company1.com that delivers mail to a bunch of local users but also to…
Mike
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How to share a SMTP domain between MDaemon and Exchange?

I need to setup coexistence between MDaemon (13.0.5) and a Microsoft Exchange system (Office 365); the two systems should share the same SMTP domain, and each one should forward to the other any message which has a recipient in that domain but is…
Massimo
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How can I relay mail to multiple SMTP servers?

We want to use Google Apps for Domains as our email service but the "corporate" office want's the emails in Exchange. I would like to set up a relay (is that the proper term) to send any incoming mail to both, Google and Exchange. That way, we can…
Richard
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