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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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Is there any risk to sending emails to accounts that no longer exist?

As mentioned in a previous question of mine, I send a lot of emails. I have calculated that approximately 2% of them are coming back to me immediately with the general text reading: 550-5.1.1 The email account that you tried to reach does not exist.…
darkAsPitch
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Smtp-Relay in SBS 2011

How to configure outgoing mail in SBS 2011? I am using Thunderbird to open more then one IMAP mailbox, but when I want to send mails it appears that relay is not supported. If I configure one username for all outgoing mails, only mails send from…
John
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MTA's poor reputation

Rather randomly only just started happening but when sending emails to certain people my emails are getting bounced back. I've set up domain keys and SPF records. I am with Just Host using an email program from their main control pannel. Thought…
Brad Parkes
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How can I configure PostFix out from our DMZ?

I'd like to configure some websites in our DMZ to be able to send emails out through PostFix to the public internet without having to pass anything to our Exchange 2010 inside our private network. Can somebody point me in the direction of how I…
Windows Ninja
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How to determine if ftp/smtp is up and running using a script?

Similiar to how these uptime monitoring servieces perform checks if your smtp or ftp server is running, how could I do this myself using python/ruby?
codecompleting
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Using multiple mail-addresses with one IMAP/SMTP account

I have one IMAP-account. Multiple mail-addresses on different domains are routed to this single IMAP-inbox (e.g. john@example1.com, john.doe@example2.com, doe@example3.com). Now I want to send mails via SMTP but want to choose which mail-addy is the…
aebersold
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Postfix SMTP server sends email without authentication

I'm using Postfix (2.3.3) on CentOS (5.7). Right now, my server seems to be acting like an open relay. If I specify a login, it works fine, both unsecured and with TLS (however TLS nags me about the invalid certificate, but I guess I just have to…
jValdron
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SMTP delivery with multiple recipients

I'm going over some SMTP log files from an open relay server (IIS 6 SMTP Virtual Server), used to collect and route all automated email within a private network, to an internet smarthost (qmail at another ISP). Using SawMill 8.5 to parse the logs,…
Mathias R. Jessen
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Qmail with AUTH CRAM-MD5

My Qmail install on Centos5 has CRAM-MD5 installed. I want to use this to an authenticated SMTP relay. Where do I specify the username and password details for QMail?
William Denniss
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Sendmail is not sending

I have a sendmail server on a Solaris 10 server that's stopped working. I can't seem to find anything about failed messages in /var/adm/sendmail. Here's what I'm seeing when I try to debug: [(root)/var/adm]$ sendmail -v me@myemail.com < testmessage…
coding_hero
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Postfix mail size counting

If I'm right Postfix counts mail size with an attachment sent to multiple receivers as one big e-mail. Eg.: User sends mail with 8 MB attachment to two receivers. Postfix thinks it's 2 x 8 MB = 16 MB mail. And when message_size_limit is by default…
meridius
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SMTP server rejects connection without SSL enabled

Setting up a new CentOS 6 server with Plesk 10.4.4 using Postfix, I am unable to send emails from any user account on port 25, 465, or 587 without having SSL enabled. If I check to use SSL in Apple Mail, on iPhone, or in Outlook, everything works…
user105613
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Exchange 2007 can not send email to the Internet

We are currently in the beginning stages of migrating from Exchange 2003 to Exchange 2007. We have got to the point where internal mail between the two systems is working perfectly with all of our testing accounts, the problem is now that Exchange…
TrueDuality
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SMTP Outbound-Only: More or less reputable?

I'm reconfiguring some mail architecture and wondering about this... For the purposes of avoiding blacklists and maintaining a good MX reputation, is it better to have: One public IP / SMTP server dedicated to outbound only e-mail Another public IP…
Brandon
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MX records for a domain with a CNAME

Given something like this: xxx.net. CNAME surrogate-xxx.net. www.xxx.net. CNAME surrogate-xxx.net. mail.xxx.net. A 1.2.3.4 xxx.net. MX mail.xxx.net. surrogate-xxx.net. A 4.3.2.1…
Ed Greenberg
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