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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Exchange 2003 mail non-delivery (NDR), spam activity? events 7002 & 7004

Windows Server 2003 Small Business Server SP2 Exchange Version 6.5 (Build 7638.2: Service Pack 2) This network has been neglected and has been having email problems for years and was on many ...
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1answer
41 views

Exchange 2010 SMTP Pipelining support not working correctly

Am trying to configure a Sophos Appliance (SEA) to handle anti-spam. Part of this service is recipient validation, which interrogates the downstream MTA, in our case, Exchange 2010, for a valid ...
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3answers
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How to send mails using a custom .NET application and Windows authentication to a distribution list that only allows authenticated senders?

This is basically a cross post from my StackOverflow question to see if I can get a server side perspective. I'm trying to send automated emails from a C# console application from machines to clients ...
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46 views

Getting unknown mail requests on my SMTP server

I set-up a private mail server on my VPS. I get a lot of mail request on the SMTP server while I did not send them by myself. I disabled the bounce mail to prevent spamming other mail addresses. How ...
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46 views

AmazonSES + DKIM + Hotmail = temperror

Although SPF is passing, I'm getting a dkim=temperror on hotmail only (it's working on Yahoo and Gmail). I'm using AmazonSES, and already have the proper CNAMES for DKIM signing on my domain at ...
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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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2answers
683 views

TLS connect failed: error:140943FC:SSL routines:SSL3_READ_BYTES:sslv3 alert bad record mac while sending mail via Qmail

I'm trying to send e-mail to one of the biggest polish hosting companies and their servers are refusing to receive it with message: TLS connect failed: error:140943FC:SSL ...
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1answer
496 views

Exchange 2013 Client Frontend connector will not accept TLS

I have a new Exchange 2013 environment running on Windows 2013 R2 with 2x Edge and 4x CAS/Mailbox servers deployed. It is deployed in a resource forest, with proper trust relationships established to ...
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118 views

CentOS 7 ec2 smtpd - Client host rejected: Access denied

I've been trying to figure this out for hours and can't quite wrap my head around it. I have a mail server on an ec2 instance running CentOS7 that has postfix, courier (authlib and imap), sasl, ...
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76 views

how to send email from an instance without using sendgrid? [closed]

My project up and beta running on google compute engine. I want to set-up email server. For that i followed http://www.krizna.com/centos/setup-mail-server-in-centos-6/ I edited /etc/postfix/main.cf ...
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1answer
50 views

Exchange 2010 not receiving some emails

Exchange 2010 not receiving emails from some senders. They receive the following email rejection message: Diagnostic information for administrators: Generating server: mail.domain.com.au ...
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25 views

Iptables SMTP re-routing on a proxy

I'm lost... Any help would be appreciated :) I have a mailserver. Unfortunately, the provider deny the smtp 25. I don't want to use ESMTP or a vpn. So here is the project : I have a dedicated server ...
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1answer
25 views

Does SendMail Support TLS Certificates With Subject Alternative Names?

CentOS 5.x Does SendMail support TLS certificates with Subject Alternative Names? I have a set of sendmail servers and would like to use the same certificate for all of them (to save time and ...
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1answer
21 views

How to make exim4 on Debian safe?

I am running exim4 on a vanilla Debian Stable system. The machine has proper DNS A and MX records. I want to use it as a mail server. SMTP with TLS already works fine for authenticated users. ...
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2answers
76 views

Postfix login mismatch sender address rejected

I'm getting the following rather annoying error message: Sender address rejected: not owned by user subscription@****.ca; from=<subscription@****.ca> to=<webmaster@****.ca> proto=ESMTP ...
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1answer
295 views

Does closed Port 25 cause mail to be marked as spam?

I have a web server where I have installed Postfix for sending emails only. All incoming mails will be handled by google apps and not my web server. Using iptables rules, I have blocked all incoming ...
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3answers
342 views

What is the difference between the sendmail submit queue and standard queue?

I'm confused on the purpose of the sendmail submit queue (by default /var/spool/clientmqueue). I think it's used to store messages when sendmail is ran in mail-submission program mode instead of ...
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1answer
54 views

Postfix SMTP server gets “550 Requested mail action not taken: Invalid IP”

I have a SMTP server named smtp-ca.mdpi.com and when sending emails to some specific chinese email domains, I am getting back: 550 Requested mail action not taken: Invalid IP<64.15.147.140> (in ...
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1answer
66 views

Centos SMTP error command not implemented

I have a vps with Centos 6.5 and postfix installed. When I want to connect to a smtp server like google or mail gun, I get the error 502 command not implemented. Can anybody help me please? This is ...
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2answers
682 views

Relay/forward only mail that originates from specific domain using postfix

I have 2 postfix servers (lets say mail.aaa.tld and mail.bbb.tld) that acts as a relays for several domains (lets say x.com, y.com, z.com) that are composed at ccc.tld. SMTP server at ccc.tld can ...
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2answers
40 views

Postfix and access restrictions for unknown clients

I'm trying to configure a postfix mailserver and I have a doubt related to parameters like smtpd_reject_unlisted_sender and that sort of things. Of course, I would like to configure my server in such ...
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1answer
20 views

sending e-mails via sendmail using virtual-users

Currently my sendmail send e-mail with following header: Received: (from www-data@localhost) I want this header to be like: Received: (from contact@mydomain) but I am also hosting multiple ...
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3answers
2k views

SMTP stress test

does anyone knows of any good software for Mac OS X or at least for RHEL/CENTOS Linux that I can run against my SMTP Server?
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0answers
40 views

Getting “5.7.1 Unable to Relay” intermittently on mails sent to Exchange 2013

I have a helpdesk system that sends mails through the local exchange server. Until a few days ago, I never had issues with it. For the last week we have started getting complaints about missing ...
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1answer
17 views

Make exim4 only send mail, do not make it receieve mail

We send email locally using exim4, but we use Google Apps to receive our email. Unfortunately, exim4 is not sending mail addressed for our domain (internal notifications) to the Google Apps mail ...
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2answers
132 views

Sending Email by SMTP IIS7.5 via php site

After my company decided to change the website we switched from old ASP.NET site to new website created in Drupal(php). The site is running locally on IIS7.5 and we also have virtual SMTP server on ...
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1answer
128 views

syslog-ng 3.5 flush_lines not working with smtp

What I want: automatic emails every time someone successfully logs into my Ubuntu 14.04 LTS server. /var/log/auth.log gets 2 lines written to it every time I login. Example: Jul 22 13:55:49 server ...
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4answers
557 views

Steps to take to improve email deliverability [duplicate]

Successfully delivering email to my clients is a pretty high priority at my company. We are of course fully opt-in, paid clients, no possibility of spam, the whole thing. The information we email is ...
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1answer
509 views

postfix RCPT TO Temporary lookup failure 451 && mail transport unavailable

i configure Postfix and dovecot in fedora 20 my problem is when set RCPT TO return me 451 4.3.0 <test@example.com>: Temporary lookup failure my postfix Configuration main.cf # postfix ...
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1answer
334 views

Interspire Email Marketer taking long time to send bulk emails

I am using Mailjet SMTP Server along with Interspire Email Marketer to send emails to a large group of users (around 54,000). I once used Mailjet's inbuilt Email Marketer to perform a similar ...
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2answers
80 views

Rate limit exim per user basis

How can I implement "rate limit" in Exim so that every user in my exim can send specific number of emails per day. List A of Users can send 100 emails per day and the list B of users can send 500 ...
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152 views

SMTP server, remove port 25 for relay communication

I have setup a SMTP server in my internal network, but I want to remove the port 25 completely since my service provider limits access to port 25. However, even using port 587 in my server to ...
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1answer
63 views

Secure postfix smtp from spammer

I run on Centos 5 with Parallels Plesk 12 and look for to secure my smtp server. When I watch at log, I see some strange line like that, which I supposed it's hack connexion. Has someone any idea on ...
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3answers
914 views

Can I send email unauthenticated to an internal SMTP server which then relays onto authenticated SMTP?

I have a back-end system which only supports sending email to an *UN*authenticated SMTP server, however, ultimately it needs to go via an authenticated SMTP server on the public internet. My idea was ...
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1answer
508 views

Debugging sendmail - dsn=5.0.0

I am getting alot of the following messages from an ISP when sending out emails. Is there any way to get more information from these ? Users are reporting that they are not receiving any emails? ...
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1answer
969 views

Postfix MySql Dovecot - SMTP Authentication Failure

Hello I have a Postfix setup with Dovecot and MySql. The server is running Debian Squeeze. The MySql server is a slave that has data pushed to it from a primary (postfix) mail server(running a ...
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19 views

Exchange 2013 Outlook “Send to cache”

Having some trouble with users changing AD accounts but their primary SMTP address is moved to the new account. Let me explain: User Andersson1 gets a new AD accout because he changes department and ...
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1answer
2k views

Centos 6 Mail Server / Can't receive e-mails but can send

I recently set up my server using Centos 6, with ISPconfig 3 with httpd, php, mysql, mail server. I can create e-mail accounts in the control panel, And I successfully can log in to the webmail, I ...
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21 views

IronPort, DLP and SMTP integration

We have configured IronPort, DLP and SMTP in my organization. Now I am getting an error message: statin - : TLS handshake could not be completed". Questions: Can anyone please tell me whether ...
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1answer
894 views

Postfix smtp mail to external hosts not possible

I administer a server (Ubuntu 12.04 LTS) running a web server and a mail server - The web server is running all fine, but the mail server is a problem. I have Dovecot installed and configured ...
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2answers
2k views

Getting the error “SMTP server cannot create a file in the queue directory C:\Inetpub\mailroot\Queue\”

We're using the default SMTP server for our websites to send mail with, but in the last day sending messages started getting this error: Insufficient system storage. The server response was: 4.3.1 ...
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1answer
488 views

Zimbra doesn't send mail via smtp relay anmore

our Zimbra-Server isn't working for outgoing external mail since yesterday. Friday I installed some updates (for shell shock and Kernel updates), restarted and it worked fine. But since yesterday ...
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191 views

Exchange 2013 (CU6): Can't find named Receive Connector referenced in Event ID 1018

I'm receiving the current Event ID's 1018 on an Exchange Server 2013 (CU6) CAS/Mailbox server causing all received/incoming mail, for all users to be stuck in the mail queue (mail is received from an ...
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0answers
20 views

Monitor outbound SMTP Xen node

Using Xen-PV on one of our nodes, looking for some suggestions on how I can monitor anyone sending mass outbound emails. May be using Tcpdump?
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1answer
61 views

Postfix SMTP authentication [duplicate]

I used this guide to create a mailserver for a small business: https://workaround.org/ispmail/wheezy. IMAP is working perfectly but i ran into an issue with SMTP and Authenticated SMTP. When i use an ...
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1answer
297 views

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 ...
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1answer
198 views

Postfix wont send mail to external email addresses listed in virtual_alias_domains

We have our main server at mail.mainserver.com with the catchall address catch@mail.mainserver.com We also have two other domains: domain1.com and domain2.com which are hosted at gmail. Gmail is ...
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1answer
23 views

Reliably identify sender in Exchange SmtpReceiveAgent

I use Exchange as a simple SMTP server and I want to take specific actions depending on who the sender is. I made a connector which allow basic authentication (auth login) and a SmtpReceicveAgent. I ...
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2answers
1k views

220 **** smtp banner while telnet mail server on a Windows XP , hmail server linksys WRT120 n router

we have setup server ,mail server using HMail server and oyr RDNS / PTr is also solved but when do smtp test from mxtoolbox.com we are getting 220 *** kind of message. our server configuration : ...
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1answer
294 views

Postfix SMTP Server fails to send messages to anyone outside the domain

Here is the result of a recent test on my SMTP server, I just want this server to send emails which used to work perfectly upto about a week ago Resolving hostname... Connecting... SMTP -> FROM ...