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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 auth do not log in on relay server

I'm trying to configure a secondary postfix to enable SMTP AUTH against my main postfix server (postfix + ldap auth + cyrus) I've follow http://www.postfix.org/SASL_README.html#client_sasl adding: smtp_sasl_password_maps =…
magiza83
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Mail forwarding to external domain - BT, Exchange 2010

Thanks in advance for any help, this is not a basic mail forwarding question there is in fact a twist. We are trying to forward mail from an address at our domain john.example@ourdomain.com to another domain john.example@anotherdomain.com these…
bettsy583
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Can't reach my alternative SMTP port

I can't seem to reach my open SMTP ports. I opened 587 and 2525, and it shows they're listening: tcp 0 0 0.0.0.0:587 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:2525 0.0.0.0:* …
Rick Kuipers
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Anti-spam: allow only authorized SMTP servers

Spam is a huge problem these days, especially spam sent with your e-mail address as the sender. I think I have a simple solution but I'd like to hear from you what is wrong with it or why it is infeasible. My idea is that a recipient server checks…
jao
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Is there a way to have Microsoft Exchange server override the from field in outgoing mail?

I need to know if it's possible on an exchange server to filter outgoing mail and override the from address in certain cases. We have to set up many Exchange users who will only be able to access exchange through the outlook web access. All their…
mic.sca
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What's the difference between Postfix SMTP server and client in regards to TLS Support?

I need to implement TLS tunneling in my Postfix so that when needed it can use TLS certification (when trying to send mails to the domain xxxx.xx, their servers will ask mine to establish a TLS session. In the documentation there seems to be two…
Amarnasan
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Reverse DNS does not match SMTP banner vs Reverse DNS mismatch

I have to make decision whether my Reverse DNS should match SMTP banner but Reverse DNS to DNS and vice versa stays different or vice versa. Which one to choose? I have an 2x Exchange 2010 server with one SMTP Sender with TMG 2010. TMG has 2 links…
MadBoy
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Need an open SMTP relay for testing

I'm developing some HTML email templates and have a internal test tool that can send out test emails to my own email address for QA purposes. Unfortunately this tool's settings page allows the mail server and port to be set but there are no…
Xoundboy
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How do I configure SMTP when using Windows Server 2003 as a mail server?

I added the "Mail Server" role to my Windows Server 2003 server, which gave me POP3 and SMTP (I really only need SMTP). I need a server on my LAN that clients can use to email out without SSL or a login (I will NOT be allowing any traffic from the…
user640
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using gmail as email relay for sendmail

I used to be able to send emails using a gmail account & sendmail configured using one of the guides on the Internet, for example: http://appgirl.net/blog/configuring-sendmail-to-relay-through-gmail-smtp/ This is a small server and I've recently…
0x4B1D
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postfix 5.7.1 Relay access denied when sending mail with cron

Reluctant to ask because there is so much here about 'postfix relay access denied' but I cannot find my case: I use php (Zend Framework) to send emails outside my network using the Google mail server because I could not send mail outside my server…
zensys
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SPF blocking some emails. How to complete disable it?

We have configured a SMTP server on IIS. We have not configured any SPF rule. Some emails are going straight to the badmail folder. Most of them have this error message: Address does not pass the Sender Policy Framework Is there any way to disable…
Rafael Colucci
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postfix specify limited relay domain while allowing sasl-auth relay

I'm trying to set up postfix to allow relaying under a limited set of conditions: The destination domain is one of a pre-defined list -or- The client successfully logs in Here's the relevant bits o'…
tylerl
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Is the legacy SMTP client submit port "456" or "465"? What is the history of this wacky port and who uses it?

I see posts on the internet, Google Apps Engine, and a few others that make mention of this unusual client submit port. Can anyone clarify which is the oddball port I should support (in addition to port 587) for end user email submits?
makerofthings7
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Disable local recipient check in Postfix

I am trying to setup Postfix on CentOS. I have configured it to use my Google apps account to send mails. Lets say I have configured Postfix to use user1@mydomain.net, which is a Google apps email. I can now successfully make Postfix send an email…
superxor
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