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.

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How do I configure reverse DNS for a SMTP server [duplicate]

We use iis 6 to send out emails for our website but some email addresses bouce backs. It only appears to be 2 addresses. There is at least 100 different email addresses sent to at the same time as ...
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(How) do you run “functional” tests on your services automatically?

Consider a simple FreeBSD machine running an SMTP server - how can I automatically verify that it's doing the right thing (e.g. accept incoming SMTP connections for certain recipients, and drop the ...
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Automatically start SMTP server in IIS?

I'm running an IIS SMTP server in Windows 2008 R2 and it can be started manually. However, if I need to restart the system, I must manually start the SMTP server. Is there a way for it to start ...
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Load Balance Mail Gateways

I am currently trying to find a way to Load Balance our 4 Mail Gateways ( Running Mail Cleaner). I was able to bring up HAProxy and use tcp mode to load balance without issue. The only real problem ...
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Exclamation marks being inserted into Emails at approx 1000 character mark

Have a .NET program that uses the System.Net.Main namespace to send an email via SMTP. Its on a customers site so from there it will go via a (series of?) SMTP relay servers before it reaches its ...
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Exchange Server vs. IMAP

I've been using a hosted exchange server environment (dslExtreme) for years. Originally, I used it w/ Outlook, but now that I have a Mac, I use Entourage. I also use my iPhone to connect to my ES ...
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Are two periods allowed in the local-part of an email address?

A third-party email gateway relay is refusing to process a message for an email address we're sending to. The address is in the format of firstname..lastname@recipientdomain.com (note the two ...
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Postfix SMTP sends to localhost, ignores MX records set to Google Apps

I have the MX records for zaltin.com set to the Google Apps domains (aspmx.l.google.com etc.). If an email is sent to kerrick@zaltin.com from most places, it goes to my Google Apps account. However, ...
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SMTP server, SPF records, domainkeys

Recently we have setup a new SMTP server to send newsletters and promotional mails to our registered users. There are 5000 users who will receive newsletters on weekly basis. We are getting bounced ...
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Mailbox unavailable, client does not have permissions to send as this sender - only the first time

Our users can send emails from our ASP.NET Web application on the click of a button. In our testing environment, there is a strange thing going on. The first time the application tries to send the ...
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saslauthd multi instance for postfix smtp authentication

I have mail server Postfix+Saslauth. I configure multiple instance for Postfix: postfix postfix-out and two instances for saslauth: saslauthd saslauthd-out Setting saslauthd is ...
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SMTP authentication failure + PAM-MySQL cannot authenticate

I am building a mail server using Postfix, and set up the authentication to check against a database set-up using Postfixadmin. I can authenticate via Courier IMAP okay, as it can authenticate ...
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receiving mail during Exchange maintenance?

I was part of a small company, and sometimes we had to bring down our Exchange server to perform maintenance. The majority of mail during the downtime would get redelivered in a timely manner, but ...
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585 views

Why is my port 25 so active?

Using netstat -na I notice that I have a lot of connections like tcp 0 0 XXX.XXX.XXX.XXX:25 YYY.YYY.YYY.YYY:13933 ESTABLISHED tcp 0 0 XXX.XXX.XXX.XXX:25 ...
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Fastest way to allow sendmail relay through smarthost?

I only want sendmail to relay through my ISP's smtp server, nothing else. How do i set it up?
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In SMTP, how does one choose between “Accept than Bounce” vs “Bounce at the edge”?

There seems to be a variety of implementations of SMTP that either immediately reject a message, and others that do an accept, then bounce the message. Operationally, the accept-than-bounce is a ...
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Outgoing only SMTP server

I want to setup an outgoing only SMTP server on Debian, so my Web-applications will be able to send e-mails via it. I don't want to use another hosts because of security and customizability of my own ...
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With regard to anti-spam practices, what exactly does a typical reverse DNS check look for?

My understanding is that a typical reverse DNS lookup will compare the SMTP hostname (provided in the EHLO/HELO command) of an incoming connection and verify that it matches the PTR record for the ...
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Spam addressed to a sender but received by everyone else

Spam's been getting through Postini lately that's addressed to a recipient (bob@example.com) in the To: field and in the headers. While this isn't that strange -- we've had spam get through before -- ...
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Anyone have a Powershell script to look up the MX record for a domain?

I want to check to see if the email addresses in my contact management system are valid and the best way I can think to do this is to get the MX record for their domain, then open an SMTP connection ...
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SMTP allows for multiple FROM addresses in the RFC. Was this ever useful, why does this exist?

SMTP allows for multiple FROM addresses on the body (not the envelope) according to the RFCs. Has this feature ever been used for a legitimate purpose? Is it safe to discard messages that have ...
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mail loops back to myself | postfix

Hi I have an issue with bounced mail it does not happen all the time but at the same time is very frequent. Most of the time if I send an email to an address that does not exist then i get a bounce ...
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Disable SMTP AUTH on Port 25

Due to PCI-DSS, we are required to disable plaintext authentication. We've achieved this by encapsulating communications between our mail server and clients with TLS on port 465. The problem lies in ...
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How do I track whether a email was successful among thousands (IIS 6, .NET 3.5)

I want to be able to tell if an email sent to a user is successful or not. I've tried looking at the SMTP logs and there appears to be no way to link server requests with server responses. So if I ...
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How to send Bulk email with SMTP server

How do email marketers get success while sending mails? Though their emails volume is very high, they can deliver mails with out any problem like spam or bounce. If we try to send bulk mails with our ...
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Will mailing lists “break” if SPF is too restrictive?

I have recently configured my own mail server (Linux-based postfix + dovecot scenario). This is just for personal use - I have no bulk mail going out, no automatically generated mail outbound from the ...
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Postfix TLS over SMTP - RCPT TO prompts renegotiation then 554 5.5.1 Error: no valid recipients

I've setup ispconfig3 on my debian six server, and here is a little smtp over ssl: The server is postfix AUTH PLAIN (LOL!) 235 2.7.0 Authentication successful MAIL FROM: lol@lol.com 250 2.1.0 Ok ...
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What is the difference between 3-digit and dotted SMTP error codes?

When looking up SMTP error codes, I sometimes see "550", or "5.5.0". (And sometimes the number in the dotted code is different.) I found the numeric codes defined in RFC 821 and the dotted codes in ...
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Custom headers in Email lost?

I have some questions about custom mail headers Does anybody know of any mailserver which deletes proprietary/custom headers when being transmitted to its destination? Is there a header you can set ...
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SMTP Reverse DNS Mismatch

My dedicated server ns382087.ovh.net resolves to 46.105.98.72 and hosts multiple domain with several dedicated IP addresses. Each new IP address is added to /etc/network/interfaces Among them, the ...
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What is preferable, “no-reply@” or “noreply@”? [closed]

Having a service that sends out notifications to users, I'm currently thinking about changing the sender email address from "info@" to something more meaningful. Since a reply never makes sense, I'm ...
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How can I configure my postfix server so reject_sender_login_mismatch doesn't block aliases of the main account?

I've recently setup postfix, dovecot, amavis and a suite of other tools using iRedMail, and I'm having difficultly authenticating to my outgoing mail server. The issue is this: xyz@mydomain.com is ...
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Simple, forwarding-only MTA?

I have a domain and a server. I’d like to have some e-mail addresses on the domain and I’d like to forward them elsewhere. I’d love to avoid running a full-featured MTA on the server, since they’re ...
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Exim TLS and Secure SMTP

I'm in the process of converting an existing mail server to support encrypted SMTP for our clients, but I've run into this brick wall with very little useful log data to help me forward. Everything ...
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Hot/Lukewarm mail server setup

We have two mailservers ("dubone" and "dubdeuce"), one does all the work while the other sits idle. We want to have a setup where if dubone is busy or down, dubdeuce can accept/reject/filter emails ...
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How to remove the SMTP address for a secondary domain from all Exchange mailboxes?

I have an Exchange server which used to manage multiple SMTP domains; now it only has to manage one. I have already removed the secondary domain from all address policies; I need to remove all SMTP ...
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Load balancing SMTP in a way that doesn't hide the source IP address

I need to load balance SMTP to handle some applications that don't know how to use MX records. I set up a Netscaler using the TCP option on port 25 and now Exchange sees the source IP as that of the ...
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Postfix, saslauthd, mysql, smtp authentication problems

Trying to get authentication on my mail server (ubuntu 10.04) running but am having trouble. I have a server with postfix for smtp setup, imap server with courier setup. My postfix authentication is ...
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How to limit amount of email sent by postfix to certain domains and control it by using mail header?

Goal I'm looking for a solution to limit rate of e-mails sent to specific e-mail operator (several Top-Level domains, all of them I know) on hourly basis. I also need some way to control the rate on ...
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Does DKIM works with subdomains?

ISP's recommend you segment your marketing and transactional emails by using different IPs. I want to start using DKIM, but since DKIM is a domain based reputation system I wonder if signing with the ...
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Using DHCP to push SMTP server addresses to clients

I noticed on the Windows DHCP service there's an option to add SMTP servers to the information provided to DHCP clients. I've never heard of this before, but it sounds useful, especially for when our ...
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How to legitimately work around ISP rate limits

A lot of ISP rate limit the amount of e-mails that is sent from a particular IP address. What is the proper way to get around that rate limit? Our company has an iPhone application that sends many ...
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Trouble with IIS SMTP relaying to Gmail

I appreciate that similar questions have been asked about how to setup SMTP relaying with IIS's virtual SMTP server. However I'm still completely stumped on this problem. Here's the setup: IIS 6.0 ...
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Mac OS X Server (10.5) mail trapped in queue

We've got mail accumulating in our Leopard Server's queue and not sure exactly why. This machine has required little maintenance over the years so I'm hoping someone here spot the obvious and save us ...
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Are there any SMTP servers that support the SMTPUTF8 extension?

RFC 5321 limits email addresses to 7 bit US-ASCII encoding. RFC 6531 (a fairly new spec) allows email addresses in SMTP commands and IMF headers to be encoded in UTF-8. This SMTP extension makes ...
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How to read the “MS ForeFront” antispam report in email header?

I'm trying to diagnose why emails I'm sending out from my server's IIS SMTP Pickup Folder are getting bounced back occasionally. One tech from a receiving company who couldn't receive the emails ...
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Exchange 2007 - One server set-up

I'm trying to set up Exchange 2007 with just one server (not the Transport + Hub configuration, just a Hub). I installed the server with the Hub Role, and it's not accepting SMTP. I changed SMTP so ...
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postfix sasl “cannot connect to saslauthd server: No such file or directory”

I try to setup postfix with smtp authentication. I want to use /etc/shadow as my realm Unfortunately I get a "generic error" when i try to authenticate # nc localhost 25 220 mail.foo ESMTP Postfix ...
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How to copy outgoing messages on sendmail

I've searched the serverfault and Google, but did not find anything related to my question yet. So, I have a customer that wants to read all emails sent by his employees. I've configured a VPS with ...
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1answer
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Flood of traffic on port 25

I am getting thousands of hits on port 25, over 400,000 connections in a day. I am using sendmail default settings on Debian 7. Mailserver is not configured. Please see below Nginx access logs ...