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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450 4.7.1 Client host rejected: cannot find your hostname

I have a Postfix/Dovecot email server which fails to deliver emails to some addresses. Here's an example of what is says: <xxxxx@board.com.ua>: host mail.da.net.ua[91.213.154.4] said: 450 4.7.1 ...
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524 views

Postfix DSN code explanation

Since few days ago I was unable to receive automatic emals sent from my PHP application. When I use Terminal to send an email to my @gmail address, everything works. When I try to send it to my ...
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1answer
69 views

Is Exchange 2010 compliant with RFC 3848

I have looked up Exchange 2010 Support for RFC Standards but do not see RFC 3848 amongst the supported standards. I do see RFC 4954 listed, which 'recommends use of RFC 3848 transmission types', ...
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215 views

postfix discard or change Message-ID header based on another header line

I want to change the Message-ID header or better yet, discard it. I know everyone is going to ask "Why would you want to do that?" because I know it sounds weird to even write it. Well I am ...
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1answer
210 views

Postfix SMTP relay server

I use gmail to receive e-mails both from my gmail address and my own domain, but gmail no longer allows you to send e-mails from your own domain name unless you provide your own SMTP server to send ...
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1answer
232 views

Postfix SMTP authenticated can send as anyone

The server correctly accepts/rejects the logins though dovecot's authentication mechanism, but after that I can pretend to be anyone when sending emails. smtpd_sender_login_maps = ...
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300 views

PHP mail() function - “from” name overwritten by Exchange Server

I originally posted this on stack overflow but was told it might be better placed here on Serverfault. I am trying to send a very simple email from a php script ...
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0answers
188 views

Does Google require TLS on port 587? Exchange 2010 SMTP has mail sent to GMAIL backed up in queue

Exchange 2010 SMTP has mail backed up in queue. Any email sent to Gmail sits in the queue while any email sent to another personal domain which has email filtering enabled errors, "asp.reflexion.net ...
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115 views

Limiting OpenVZ SMTP Per Hour

How would I limit SMTP connections per hour on the host node for a /24 block? For example, I want to limit it to 50 emails per hour. Thanks
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169 views

Postfix forward incoming emails to mailin

I've setup the smtp server using postfix with dovecot on mail.example.com server running on port 25. And then I've also setup another smtp server using mailin (http://mailin.io) on mail.example.com ...
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97 views

What is X-DKIM header for?

There are some emails with an X-DKIM header (next to DKIM-Signature) like this: X-DKIM: Sendmail DKIM Filter v2.8.2 DOMAIN SOMEVALUE However I am unable to find decent documentation for it. What is ...
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145 views

Configure email SMTP Server on Apache2 [closed]

For a while we decided to use another Server (VServer "B") for our Mailserver. I transfered all email accounts and mailbox from VServer "A" to VServer "B". VServer "B" runs well and the clients are ...
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323 views

hMailServer SMTP installed in LAN, clients in LAN can send Email but clients from the Internet cannot

I had checked the troubleshooting guide and many posts here and could not find solution so far. I had setup a network in Azure Cloud with 2 VMs, 1 of which is domain controller and the other is Web ...
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1answer
250 views

SMTP errors with iOS devices

I'm trying to diagnose why when an iOS device like an iPhone or iPad is set up to use email with our server for the first time, these errors occur. We choose "Other" from the initial set of choices ...
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1answer
22 views

RFC5321 “receiver should check […] reply code” (why?)

In SMTP commands are sent by the sender and responses which all begin with a numeric code are sent by the receiver. but then there's this bit: RFC5321 sec4.2 Whenever possible, a receiver- SMTP ...
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222 views

Postfix: sendmail (php-cgi) with different IP as authenticated SMTP Users

my Postfix-Mail Server is delivering two main types of mails Mail recieved from php-cgi (sendmail), localhost relay Mail recieved from authenticated SASL SMTP Users Is it possible to define a ...
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1answer
885 views

postfix multiple IP SMTP banner

I've installed postfix 2.11.3 and we have multiple IP addresses on our server which we want to host two domains, isolated and running on their own IPs. domain1 unix - - n - - ...
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192 views

How do I configure Postfix to accept SMTP for local users with “@” (at sign) in logins?

I have an Ubuntu 14.04 server at mydomain.com with a bunch of users with @domain in login, like us.er@mydomain.com. Each of them has an "pseudo" account us.er-mydomain.com with the same uid, passwd ...
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1answer
82 views

Exchange SMTP authentication issue with spammers

I have a single Exchange 2013 server with all the roles and it looks like it's being used by a botnet. It is sending mails every 10 minutes to a specific domain from a specific user. It is not an ...
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53 views

CentOS/sendmail = How to prevent emails from getting “defer” when sent from php mail() function? [duplicate]

I am working on a server running on CentOS (goDaddy VPS). I have WHM setup on it. And I am getting a lot of delays in emails being sent from php's mail() function. I am looking at the Email > Mail ...
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1answer
83 views

iPhone SMTP Server errors with Regional Cell Carrier

I run an email server (CommuniGate Pro) under Red Hat Linux for our organization of about 200 employees. Many of our employees use their phones (iPhones 5 or later), to get their email. Some use IMAP ...
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1answer
84 views

Rewrite sender when relaying to provider server [duplicate]

I am trying to relay email thru my provider that has a mail server for my domain (xxxx.com). My postfix is configured as follows: relayhost = [smtp.xxxx.com]:25 the server requires authorization, ...
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41 views

Can't connect to any SMTP server from neither of the Macs in the network

For a few days now we have been unable to send out any E-mails from various Macs in the network to various SMTP servers. No changes to any hardware or software have been done in the recent time that ...
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1answer
249 views

ERROR: account.INVALID_ATTR_NAME (invalid attr name: invalid attr name) - zimbra

I followed this link to configure outgoing SMTP mail for Zimbra. In the step zmprov ms <server> zimbraMtaSmtpSaslPasswordMaps lmdb:/opt/zimbra/conf/relay_password zimbra show me the error's ...
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180 views

IIS SMTP SmartHost configuration failing to send for a specific domain recipient

I have an web application sending email (pickup folder) using the local IIS6.0 SMTP server. It is configured to send email via Rackspace as a SmartHost. We have a problem sending emails to a ...
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2answers
44 views

E-mail reputation using our domain as the from sent by e-mail marketer

My boss wants to send a marketing e-mail to a large group of our customers. I personally feel that it's outside of our core business and don't support it, but that's about all I can do. Normally the ...
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282 views

EXIM re-routing mails through Mandrill to circumvent Gmail rate-limit

I have two domain (lets assume example.com and example.net) where we have 300+ mailboxes. Users email themselves and outside the company. Most of the emails sent outside the company are to GMAIL. ...
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2answers
2k views

How do I configure PostFix to allow phpmailer to send out email through it?

I have setup postfix on CentOS and trying to configure phpmailer with smtp authentication. Phpmailer will only work if i put 0.0.0.0/0 under mynetworks in postfix main.conf mynetworks = 127.0.0.0/8, ...
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59 views

How can I explicitly disable TLS when sending to one specific recipient?

I have a SendMail 8.14 server deployed in the middle of an SMTP workflow (Outbound mail looks like Exchange -> SendMail -> Appliance -> Internet) I have TLS configured for the first three hosts. ...
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1answer
271 views

How to connect ubuntu to external smtp on port 587?

I have a fresh ubuntu server installation with no firewall and want to setup ssmtp to an external smtp server (e.g. smtp.mandrillapp.com:587), however, I couldn't get my server to connect to any ...
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164 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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195 views

SMTP proxy (relay) with SSL

Short question I need some kind of SMTP proxy server which does not verify passwords and directly pass credentials and data to a target server. The target server uses self-signed certificate so I ...
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1answer
94 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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1answer
95 views

What's the proper way to setup a domain name to not accept email?

RFC 5321 sec. 5 states that: SMTP clients must look up for an MX record; if no MX record for domain is present, look up for an A Resource Record (RR), and if such record is present, treat it as an ...
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28 views

Windows server | HmailServe | Relay

My setup: I am using PHPMailer (smtp) to send out emails via my websites. I am using a windows 2012 server as my mail server which is using Hmailserver. I am using Mailgun to relay my emails. Things ...
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508 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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2answers
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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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141 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
61 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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1answer
81 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
394 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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2answers
410 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 ...
2
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1answer
405 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 ...
2
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1answer
245 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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468 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 ...
0
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1answer
28 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
588 views

Postfix + Php Mail() VS Postfix + SMTP

Most CMS (Joomla for example) comes with php mail() as default and has the option of changing it to SMTP if we want. I will be setting up both the webserver and mail server (Postfix) in the same VPS ...
2
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0answers
183 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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236 views

Use nginx as reverse proxy for outgoing mail

We have a production server running a singlepage web-app and a separate proxy server, for security reasons. Every request to our web-app is handled by our reverse proxy (nginx) on the proxy server. So ...
0
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1answer
30 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 ...