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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Office 365: 'client smtp submission' suddenly starts failing. How to diagnose client auth error?

Since a few days, my application fails sending SMTP email. The app is in fact a scheduled task (which is running on my local machine, written in C#, using SmtpClient) and occasionally needs to send ...
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1answer
82 views

How easy is it to sniff the SMTP port of webserver to capture mails

I've got a very basic question that I don't know the answer for. Our company owns a webserver that runs multiple websites and works as a mail server for these websites as well (e.g. to send contact ...
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1answer
153 views

SBS 2003; Exchange 2003 can't receive mails without SMTP connection but without POP3 connector [closed]

i hope you can help. I'm losing my mind. I'm not a specialist in SBS but i have a huge problem. I wanted to replace the mircosoft pop3-connector with popcon because i was told that several mails ...
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2answers
95 views

Correct FQDN Setting?

I can see from SMTP logs that some mail is being rejected OutboundConnectionResponse SMTPSVC1 Sxxx - 25 - - 504+:+Helo+command+rejected:+need+fully-qualified+hostname 0 0 69 0 47 SMTP In ...
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1answer
102 views

Where does e-mail header “Received: from…” come from? [closed]

I sent myself an e-mail from my server to my gmail account, here is one of the headers (partially redacted): Received: from cpvds3xx.xxx.com (dev1.xxx.com. [209.51.132.xxx]) by mx.google.com ...
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2answers
877 views

Why is email being delivered normally despite an SPF “hardfail”?

I'm trying to figure out why forged email is being delivered to major email providers (gmail.com, outlook.com) even though email is marked with an SPF hardfail. The email is also delivered to ...
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1answer
414 views

hMail delivery queue full with unsuccesfull spam

Since a day or two the mail delivery queue of the hMailServer is exploding because someone is trying to send spam via this server. Though the e-mails aren't successfully sent it fills up the mail ...
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1answer
66 views

Is extra “Received by” in mail headers bad and can I remove it?

I use our own VPS web and mail server to send out a newsletter regularly to 50,000 addresses. I am trying to improve deliverability and was looking through some of the thousands of bounce emails. One ...
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1answer
33 views

Scanning server results in warning about STARTTLS [closed]

After scanning our webserver, I've got this message: The remote SMTP service, support the user of the 'STARTTLS' command to switch from a plaintext to an encrypted communications channel. As I ...
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2answers
2k views

Exim on Centos - Configuring gmail smtp

I want to set up Exim to send the mails through my gmail (actually my domains google apps). I have added the router, transport and authenticator. Specifically: gmail_route: driver = manualroute ...
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0answers
324 views

Configuring Monit to Send Mail through Office365

I'm trying to configure monit to send emails through Office365. Here's the relevant configuration: set mailserver smtp.office365.com port 587 username "username" password "password" using ...
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145 views

Undeliverable SMTP email not saved to badmail folder using IIS6.0

I am testing my SMTP virtual server hosted in IIS6.0 to verify that when an email cant be delivered and cant be sent back to the sender, then I need to see a copy of the Non Deliver Report in the ...
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2answers
106 views

Email flagget as spam or rejected by recipient mail server

I have configured smtp service on a windows 2008 server. All the emails sent by the smtp service are flagged as spam or they are rejected by the recipient of the email. In the header of the email I ...
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1answer
230 views

Using alternate server for specific subdomain - DNS settings

I'm trying to set up DNS records for a domain name, such that mail.domain.com uses a server that is different from any other request to *.domain.com. As I've been going about trying to figure out how ...
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0answers
4k views

550 5.7.1 Message Rejected due to content restrictions

I have a server that for some reason, out of the blue is now having a huge amount of its email being rejected, coming back with 550 5.7.1 NDR's or various derivatives thereof. This just started ...
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0answers
179 views

Handing E-mail Bounce Back in IIS, Setting up SMTP

Our servers send e-mails from @example.com to customers, clients, etc. We use Google Apps for our domain to send and receive additional e-mails from @example.com. Now, we're trying to handle e-mails ...
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2answers
9k views

Postfix - Host or domain not found

I just installed Postfix on my ubuntu, on a local network. On this network, I have an Exchange Server (using domain mail.example.com). I had a problem sending an email to a local address : ...
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0answers
25 views

IIS SMTP deleting messages that failed to send

Windows Server 2008 R2 with IIS 6.0 SMTP I recently ran into a smarthost permission issue where my IIS mail server couldn't forward certain messages to it. Basically, the user authenticated for the ...
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1answer
235 views

Send email through Gmail SMTP to avoid local delivery attempts?

Background We use Google Apps for email with our domain example.com: [ec2-user@example ~]$ dig MX example.com … ;; ANSWER SECTION: example.com. 300 IN MX 1 ...
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1answer
141 views

Restrict SMTP for localhost only

How can we restrict SMTP service to be used on localhost only? Our websites are using localhost SMTP but we do not want any mail clients to use our server on SMTP port. Our server is Windows Server ...
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2answers
542 views

Domino always server fails to send SMTP email at first attempt

In our logs, we find the below: Router: No messages transferred to fakedomain.com (host mx.fakedomain.com) via SMTP: The server is not responding. The server may be down or you may be experiencing ...
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1answer
419 views

Unable to Connect to SMTP Host

I am trying to configure Postfix on CentOS 6 server, and the problem is that I cannot receive mails. I tested it on http://mxtoolbox.com/ and I get an error Unable to Connect to SMTP Host. I check ...
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1answer
226 views

What are the security risks with running an SMTP server? [closed]

I'm running Windows Server 2012 and I would like to set up an SMTP server to work with my hosted websites. I've previously installed various roles on my server which have resulted in exposing security ...
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1answer
212 views

Postfix mail from outside not received

I am using Dovecot with Postfix and virtual user/mailboxes. Everything works fine accepting receiving mail from outside (other domains named as the mailserver) I am able to: - send mail from my mail ...
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1answer
208 views

Should I listen for SMTP on both 25 and 587?

I was setting up haraka as our mailing server, and for outbound email, it suggests moving to port 587 for SMTPS auth support. However, I'm unsure if I should be running 2 instances of haraka on ...
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1answer
2k views

CentOS postfix smtp server connection refused from outside

I am quite stuck with my postfix/smtp configuration on my CentOS machine. I setup a mail dns mail.domain.tld, configured in the postfix main.conf file and tested locally on the server by connecting ...
2
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1answer
88 views

SMTP routing cases: same @domain as sender and different @domain

I would like to know what is the difference between sending an email to the same @domain as the sender and sending to a different domain. I cant really find a detailed explanation on the web. From ...
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1answer
107 views

Postfix only delivering mail locally (instead of correct destination)

For whatever reason, postfix cannot send email to my google apps account. It says the message is sent, but I've confirmed with google apps support that the message isn't being received. (Thus it is ...
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1answer
181 views

Exchange 2007 rate limiting

I have devices on the network that send out email alerts for misc things. The other night there was a condition that caused one of the devices to send a few thousand emails to a couple of internal ...
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1answer
370 views

check_smtp not working when scheduled

I am trying to set up a new check in Nagios 3.5.0, making sure that my mail server is contactable on port 25 over the internet. I am using the check_smtp command. When I run this command from the ...
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1answer
298 views

postfix deliveries per connection

hope you can assist me in this case. I am administrating an Postfix server which is used for newsletters. Recently one of the major recipient domains changed their policies to only accept one email ...
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44 views

Issue with Russian Characters using IIS6 SMTP Relay

We have an issue where we have an issue with Russian Characters in the body of emails when using IIS6 SMTP Relay on Windows Server 2008 R2. The relay points to an email provider. The characters ...
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1answer
78 views

Using mime_header_checks to ACCEPT instead of REJECT?

I'm pretty well versed in using header_checks/mime_header_checks to refuse smtp mail in Postfix, but now I think I've gone off the path of righteousness; I'm trying to suss out a way that I can refuse ...
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123 views

Outlook on Exchange: Why does it mangle return address for some email?

We have seen this too much in multiple Exchange environments, and need some guidance. When we email (using simple mail client app) to certain Exchange/Outlook sites, when those sites hit Reply, our ...
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0answers
106 views

SMTP on Windows Server 2008

Okay, i know that the built in SMTP server role inside Server 2008 is a little beleaguered; however, using resources here (stackex) and from msft I've worked through the issues I've been able to ...
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1answer
218 views

What do I need to be able to send mass SMTP email efficiently? [closed]

I am creating a web application that allows users to send broadcast emails to a list of subscribers. Essentially, it's a mass emailer and autoresponder, like AWeber or Constant Contact or MailChimp. ...
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9 views

Limit esmtp authentication on courier mailserver to certain IP addresses

I would like to limit authentication for users outside of our company network. It is possible to block authentication based on networks or by selected users? Thank you for any tips.
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1answer
217 views

5.7.1 relay access denied when accessing from vb.net application

I am developing a program in vb.net which needs to connect directly with my mailserver (postfix) to send emails which will be directed towards email to sms transmissions. My mailserver is otherwise ...
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1answer
223 views

Change SMTP server for SBS 2011 Self Monitoring Reports

SBS 2011 sends daily/weekly/instant reports from the account SBSMonAcct@. It uses localhost as the SMTP transport as being SBS Exchange is usually installed. I want to use an external SMTP server. ...
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2answers
115 views

Can MS Exchange 2010 act as an SMTP server?

We have a brand new Exchange 2010 based mail server and need to send e-mail from a remote website and some internal apps (like backup tools etc.). Can Exchange 2010 act as a SMTP server or we shall ...
0
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0answers
145 views

Incoming mail flagged as spam

A customer of my company can no longer contact us via mail. Our mailserver keeps bouncing their email as spam. I've already contacted them but they say the problem lies with our server, not with ...
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1answer
65 views

Allow spoofing on postfix server

I'm trying to set up help desk software which requires the ability to change the headers of a message (aka 'spoof' it). Right now, my mail server is configured to use SASL and requires authentication ...
1
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1answer
49 views

Sendmail dropping domain name from the username

I'm setting up Dovecot with Sendmail and I almost have it working (I think). The username for the account is a full email address such as "username@domain.com". What seems to be happening is that ...
1
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1answer
40 views

Simple Email Fowarding

Is there a program that handle smtp that has one and only one function: foward email from one email address to another email address? I know that this can be done using virtusertable with sendmail. ...
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2answers
364 views

Postfix, TLS and StartSSL certificates

I recently changed my postfix installation to use TLS with a certificate issued by StartSSL. I then ran SMTP and TLS checks with no errors or warnings. Everything seemed to work fine. My problem now ...
2
votes
1answer
100 views

Exim retry is Message based instead of host based? why

from what I understand exim retries are supposed to be HOST based, NOT message based. This seems to make sense to me; if a host's server is overloaded or otherwise telling you to "delay sending ...
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68 views

How can I prevent Sendmail from cutting off SMTP error responses from a recipient MTA in maillog?

CentOS 5.x | SendMail 8.14 I've noticed that Sendmail will occasionally cut off SMTP error responses in logs. For example: Jan 10 05:55:55 foobox sendmail[20998]: s1CStsdli020998: ...
2
votes
2answers
92 views

how to Dedupe email messages in exim mail server (Linux)

If a User is listed in multiple aliases or multiple mailing list or groups a message is sent to more than one of the aliases, mailing list or group the end User will receive multiple copies. How to ...
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1answer
690 views

Postfix smtpd not listening 'Unable to Connect to SMTP Host'

I set a postfix + cyrus-sasl + cyrus-imapd mail server on my CentOS 6.5 x64 server. After I finished the settings, I found that I can send internal emails and send emails to other mailboxes like ...
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1answer
382 views

Postfix SMTP authentication per domain

Is it possible to configure SMTP authentication on Postfix with different user/pass credentials for different domains? So, I have a MTA that relays emails from ~20 different domains. When sending ...