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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77 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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40 views

Is reverse DNS a good method for promoting grey IPs from trusted domains to white?

I'm trying to set up a mail server using OpenBSD, OpenSMTPD, spamd, and pf. The first problem I've encountered is that many large webmail providers - like Gmail - will retry delivery from a different ...
3
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0answers
255 views

Recipient address rejected: User unknown in virtual mailbox table

I have a dedicated linux server running Plesk 12.0.18. On this server, I have running 61 subscriptions, only 1 have this problem. When I want to send an e-mail using roundcube from 1 of my ...
3
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0answers
286 views

How to identify the user/computer that is relaying spam through a mail server?

For the past couple of days, at certain intervals, a huge load of email is dumped on my Exchange 2003 server and relayed out until it gets blacklisted everywhere. Nothing like this happened for many ...
2
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409 views

nullmailer swaps sender and recipient

I want to send emails from my server through external mail server. So I installed nullmailer as one of simpliest MTA in Debian 7 x32. My /etc/nullmailer/remotes: smtp.example.com smtp --user=sender@...
2
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305 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 ...
2
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0answers
315 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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1k views

When does Postfix not perform lookups in virtual_alias_maps?

I'm having a real pickle of a problem: I have a Postfix 2.6.6 / CentOS 6 server that's set up to forward mail from specific aliases to specific destinations. This is done through a mysql ...
2
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30 views

I need to set-up the blocked machine to relay to the unblocked machine using a different port

I have two Windows Server 2003 machines sitting in a network. Server B has port 25 open and can relay emails to the local network's smtp server. Server A does not have port 25 open. How can I set it ...
2
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326 views

Forcing IIS virtual smtp server to verify outgoing TLS certificate

I am in a situation where a web application is using the IIS virtual SMTP server to send out email. The IIS virtual SMTP server is then configured to send all mail out through a smarthost, over TLS ...
2
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273 views

How can I change the default email address format type for replies on blackberry?

Exchange 2007 BES 5.0.x Hello all, I'm trying to help a colleague with a technical issue. I apologize in advance for not having all of the information. I'm looking for some advice on where to ...
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14 views

IIS 6 Sending rules

I need to send all emails out as normal with the condition of gmail.com & gmail.co.uk emails. Which need to go via the google smtp relay service. Is this possible to setup on IIS 6? Basically 2 ...
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346 views

Using PHPMailer on Hostgator (timeout when try to login into SMTP server)

Solved: The problem was that to use the service through hostgator, for some reason the user must log in using main dsn name and not the SMTP domain name. I was using the simple PHP mail() function to ...
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72 views

Postfix with Dovecot Disconnects after STARTTLS on Port 25

I am having a lot of trouble setting up the Postfix to do STARTTLS. It seems that I could successfully send outgoing mail using Thunderbird. However, I can't seem to get the Postman SMTP for Wordpress ...
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39 views

Mail subdomain not connecting to Windows Server Virtual SMTP via Telnet Client

I trying to set up subdomain (e.g mail.mydomain.com) for use with a virtual SMTP server running on windows server 2012 SP2. I’ve tried to telnet with the command ‘telnet mail.mydomain.com 25’ but it ...
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246 views

Postfix couldn't send mail on Ubuntu VPS server, network unreachable/connection timeout

I have a problem with postfix. When I am trying to send some mail from commandline, I get: Feb 14 12:44:35 some-server postfix/smtp[1022]: connect to gmail-smtp-in.l.google.com[2a00:1450:4010:c07::1a]...
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24 views

Postfix intercept emails with apache server

I have a server(using postfix) to relay emails to a smtp server. I am tasked with separating the emails by the domain(2 to be exact) to send to 2 separate smtp servers. The idea was to use transport ...
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113 views

Windows Server 2012 R2 - SMTP Relay - Connection Dropped by Remote Host

We setup a relay server for Office 365 on a Windows Server 2012 R2 instance roughly a year ago. Everything has been fine until the past week when the relay appears to lock up and e-mails continue to ...
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117 views

Exchange 2010: not receiving NDR when sending email using SMTP to none existing external mailbox

We are sending email using smtp port 25 in a local Exchange 2010 server We do not set username nor passwords in the SMTP connection, only "form" address. Mails are sent to external recipients after ...
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31 views

Postfix STARTTSL works in LAN but not from external (centos 7)

if I connect in LAN on port 25 to my mailserver it offers STARTTLS telnet mailserver.com 25 Trying 192.168.0.x... Connected to mailserver.com Escape character is '^]'. 220 mailserver.com ESMTP ...
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221 views

hMail Server SSL Certificate Verify Issue | TLS/SSL handshake failed

I will tell you my situation step by step and ask me any necessary questions and help me to fix hmail certificate issue. First of all : 1- i am using a windows server 2008 - r2 2- latest hmail ...
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115 views

How to detect SMTP AUTH attempts in Fail2Ban?

I have a Fail2Ban jail that monitors failed SASL authentications to my Postfix SMTP server. When this occurs, /var/log/mail.log contains these three lines: postfix/smtpd[32591]: connect from unknown[...
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402 views

Outlook.com rejects: 550 SC-001 (BAY004-MC5F13)

I am operating a cluster of 3 dedicated machines for a webapp, each of those uses sendmail as MTA. Hostnames are node1.domain.com node2.domain.com node3.domain.com Unfortunatelly outlook.com rejects ...
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13 views

Are there issues in whitelabling a SMTP server (not mine) with an A record that doesn't match 200 helo?

I know that a CNAME and a MX record can't exist on the same host. In this scenario I'm using A records to manage SMTP for 350 DNS domains. companyA.com MX myAlias.whitelabel.com companyb.com MX ...
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61 views

Postfix permit localhost use plain login

I have postfix 2.11 setup on Debian jessie with Dovecot SASL and I require encrypted login mechanism to send mail via smtp. For this purpose in the main.cf I've smtpd_tls_auth_only = yes option set. I'...
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46 views

Email validation fails on HELO / RCPT TO commands to records

I'm migrating a mailing service from a server to another. Before setting up new mailing list I wanted to process it through an email validtor I've setting up on the server. I basically used this tool ...
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223 views

Setting up nginx to proxy (adding SSL) SMTP with authentication

In my organization we are migrating a certain web+mail setup, and I think that maybe nginx can be suited to do what I want, but I cannot fully understand the official documentation. I have a certain ...
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186 views

IPTables, route specific port through VPN

I'm running my own mail server at home on a dynamic IP. Dynamic IPs are often blacklisted, so I currently send out mails through my provider's relay. I want to change that to sending mail directly, ...
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325 views

Exchange sending QUIT after 220 ESMTP Status Ready

I am hoping someone can help with an issue we are experiencing between our smart host and our Exchange 2010 Server. When our smart host tries to deliver email to our exchange, we are met with a 451 ...
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379 views

SMTP error : Remote host said: 550 5.7.1 At least one FROM header address not allowed to send mail from IP ADDRESS

We are developing an email sending app, and we allow our users to specify the From: header their emails will be sent from. Let's say our domain is mydomain.com and our client domain is clientdomain....
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129 views

SMTP delay when sending mail from Centos

I am encountering long delays when trying to send mail with swiftmailer using 1and1's SMTP server. there is a 19 second delay everytime as shown below by tcpdump: 21:54:50.784747 IP (tos 0x0, ttl 64, ...
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407 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 mail($to,$subject,$message,$headers);...
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0answers
1k views

vCenter Server Appliance email's not reaching smtp server

Email's being generated from my test alarms in vCenter are not being forwarded to the proxy / SMTP server configured. I run tail -f on the mail log file when generating a test alarm and I can see the ...
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0answers
342 views

Exchange 2010 – Multiple Smart Hosts

A client has Exchange 2010 which, up to now, had a single internet connection. They were sending email via a smart host run by their ISP. It was working OK. We have put in a second internet ...
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0answers
1k views

How Do I Configure Nginx To Communicate with SMTP Server?

I'm an application developer and have little knowledge on sysadmin / server configuration tasks. I have an nginx server communicating to a Flask web application through uWSGI on a VPS. I'm trying to ...
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0answers
2k views

Diagnose SASL LOGIN authentication failure with postfix and sasldb

I am trying to configure a Postfix SMTP server on my personal machine (ubuntu server) using sasldb2. So far what I have set up works well with the test command: testsaslauthd (however it may be ...
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2k views

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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257 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
27 views

Is it possible to prevent emails being sent from an address absent from the AD user's account?

I'm using Exchange Server 2003 on a Windows Server 2003 which is also a domain controller. If a client connects through SMTP using his AD username and password, he can send email from any email ...
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676 views

Exim SMTP Smarthost Setup

I used these settings to set up exim to use gmail as a smarthost, which worked. However, I don't seem to be able to use these settings against other smtp servers, such as Yahoo or Fastmail (both with ...
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460 views

Set Windows Server 2008 R2 SMTP for Opportunistic TLS

I use a Windows 2008 R2 server for sending (relaying) outbound emails to clients. Many of these clients are now requiring TLS connections to send them email. To date I have set up a an SMTP "Remote ...
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3k views

How to access Apache Tomcat running on Windows Server 2012 (alongside Microsoft SMTP service)

I am running Apache Tomcat as my only HTTP server on Windows Server 2012. Tomcat has been installed as a service and is bound to port 80. The server.xml file has had address="0.0.0.0" added to the ...
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483 views

4.4.1 Timeout in 10 minute intervals SMTP on batch email jobs

I am running a job that uses SMTP and it can run in excess of an hour, emailing the entire time. It's not my code but a workflow based app so I just get a form to configure the mail server, subj, msg, ...
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325 views

Mail stuck in queue folder using IIS 6.0 SMTP server

I have finished setting up my server but when I sent email it got stuck in queue folder. This was a test email which I put in pickup folder. So I checked my log file. I have pasted the log files here....
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2k views

451 Timeout trying to verify RCPT errors from some external contacts

Outside contacts at two companies report messages they sent to us return with the following message: 451 Timeout trying to verify RCPT validemail@ourdomain.com for domain One of the companies ...
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1k views

What are the values of Exchange's XSHADOW and XQDISCARD commands?

Shadow redundancy is an Exchange-specific feature (beginning with Exchange 2010) that provides a measure of fault tolerance when relaying email messages with SMTP. The sending Exchange server sends ...
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1k views

530 5.7.1 Client was not authenticated Exchange 2010 for some computers within mask

We have a classic problem with Client not Authenticated but with a specific twist: We have an Exchange 2010 cluster, let's say EX01 and EX02, the connection is always to smtp.acme.com, then it is ...
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559 views

IIS 6 Smart Host Outbound Security

I'm using the IIS 6 smart host setting to forward all email sent through IIS to SendGrid. It works fine if I set the Outbound Security and smart host settings at the top level of the Default SMTP ...
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0answers
223 views

Disable local delivery ONLY for authenticated users in Qmail

We are moving some mailboxes and servers. I'm looking for a way to use remote delivery (with normal MX lookup) instead of local delivery ONLY for authenticated users, in Qmail. connection to port 25 ...
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489 views

Stop IIS SMTP Server from sending “Delivery Status Notification (Failure)”

I have set the BadMail directory and the 'Send copy of Non-Delivery Report to' fiels is empty but, somehow I am still receiving the failure messages. Is the a way to stop the failure messages?. I am ...