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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Non-received mail return code 5.7.0 Access denied

I am experiencing strange problems on our Exchange servers (exchange 2003 SP2); lately some domains can't communicate with our server. We are able to send messages outside without any problems, but ...
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16 views

port forwarding for mail server

How should look port forwarding in my router, if I have mail server in my network along with PC's? I want to be able to receive and send messages from server. Will not port forwarding break my IMAP ...
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Server Security - Stop sending spams from server [duplicate]

My server is sending spam emails because of which my IP is blocked at some servers. Can any body please suggest what security measurements should be taken? Also Norton Safe Web has analyzed my site ...
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16 views

535 error from gsmtp

I am using Erlang and its esmtp library to send emails from my application. It used to work OK and still works fine on the development machine. Unfortunately several weeks ago it stopped working on ...
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1answer
11 views

Postfix canonical map for forwarding

Because of problems of IP/domain reputation (my server and domain very recent), I had to use Amazon SES as SMTP relay to be able to not have my mails flagged as spam. My setup with Amazon was working ...
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6 views

SMTP IIS getting 452 status

I'm receiving emails on a Win 2008 R2 server via SMTP. Some of the emails are rejected with status 452, while others are accepted. I've disabled all size limits, including drop disk quota, but the ...
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12 views

How to connect to mail server in C [migrated]

I tried to make a connection to my mail server which is in local area network. The ip of mail server is 192.168.1.1. So, I tried the following program to test that. Program: #include<stdio.h> ...
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15 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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46 views
+50

SMTP server ready but 'Could not connect' error appears

I have set up a web server to use an SMTP server to send out emails. Here is a section of the log entries generated when I try to send a test email: 2016-02-03 10:20:01 CLIENT -> SERVER: STARTTLS ...
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9 views

Postfix smtp send (from Email + ip ) condition if not reject . how to?

Dear friends, i have case that require that i should allow some application to send without authentication (done mynetworks). my problem if i allowed any ip to send using mynetworks it can send from ...
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1answer
29 views

How to move the Inetpub\mailroot folder on SMTP Windows Server 2003 where Exchange isn't installed

Can anybody enlighten me on how to move the C:\Inetpub\mailroot\ directory to a different location i.e. D:\ on a Windows 2003 Server that does not have Exchange installed on it? The only modifiable ...
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1answer
40 views

Do any versions of Microsoft Exchange Server support RFC 5336 / 6531(Internationalized mailbox names)?

https://en.wikipedia.org/wiki/Extended_SMTP#SMTPUTF8 The SMTPUTF8 extension allows UTF-8 encoding in mailbox names and header fields. This provides the capability for sending email to ...
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2answers
16 views

Why does DMARC operate on the From-address, and not the envelope sender (Return-Path)?

Several emails sent from my webserver to a Gmail address, where the From: address is websitevisitor@gmail.com, have been marked as spam by Gmail. The From: field is populated from form data, and ...
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1answer
37 views

Purpose of SMTP message routing (relaying)

I am wondering why SMTP is designed in a way which allows intermediate MTA on the path of a message. According to RFC 5321, The objective of the Simple Mail Transfer Protocol (SMTP) is to transfer ...
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11 views

Rewrites message headers from remote SMTP clients to a local address

Question in the title, is it possible to rewrite message headers from remote SMTP clients for emails send to local addresses? (using Postfix, Exim, or anything else)
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15 views

disable SMTP relay/auth domains

I am using postfix 2.8.x, for some reason I want to disable SMTP relay/auth for some domains. I have studied from postfix page for configuration and I am guessing to use smtpd_relay_restrictions, ...
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1answer
18 views

Added second Exchange 2010 server, getting delivery delayed to external users

We have on Exchange 2010 server in our domain, on-premises. We added a second Exchange 2010 server in our cloud environment, which is also part of our domain and connected with a site-to-site VPN ...
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12 views

Configuring IIS 7 SMTP settings via powershell

I need to touch up the list of IP addresses that can relay through my SMTP virtual server in IIS. I've been trying to get a handle on what cmdlets and to use in my script but am struggling a bit. ...
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11 views

IIS 6.0 SMTP not sending NDR to user from web application

We have a web application that is configured to use an internal mail relay running on Windows Server 2012 R2, IIS 6.0 for the SMTP though. I just put this server in place as a replacement for an old ...
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0answers
15 views

How do I configure the listener binding address for python 2.7 smtplib running in a windows environment?

I am setting up an application called openemm which uses the python 2.7 smtplib to handle smtp transactions. My outgoing mail works fine but smtplib is not responding to incoming requests on port 25 ...
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1answer
22 views

Is it possible to use CDO libraries (classic ASP) to send mail to Office 365 / Exchange Online?

I'm working on a migration to Office 365 / Exchange Online for a SMB company which until now has been running a local Exchange 2010 server; we're talking about ~25 mailboxes here. However, there's a ...
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27 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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2answers
34 views

How do I send (legitimate) email on a dedicated server as appearing from different domains?

We need to send email using PHP's mail() function (Actually CakePHP, which wraps that function) directly from our dedicated server (app.ourserver.com). We would like to send mail from ...
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1answer
22 views

SMTP network ACL on AWS

I have a very restricted ACL for my VPC. We have a public subnet and a private subnet, each subnet has its own individual ACL. What I don't understand is why the following ACL works for sending email ...
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24 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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16 views

Postfix smtp relay to Office 365 for certain sender-domains

I'm running Debian Wheezy with Postfix 2.9.6 and I'm trying to enable the smtp relay for some certain sender-domains for office 365. I whitelisted my IPv4 for smtp relaying on the exchange server: ...
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1answer
27 views

Use two different mail servers for a single domain [closed]

sorry for my english, I have used Google Translate. I have a Arsys host (an ISP host from Spain), which gives me 50 email accounts with 6GB of storage each. I have about 6 accounts of those who need ...
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2answers
33 views

Postfix admin/Postfix: Send e-mail from an alias

I use postfix (basically postfix admin) to define my e-mail inboxes and SMPTs. Say I have a one e-mail inbox: maininbox@mydomain.com Now I have a few aliases. Say I have the alias: ...
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1answer
11 views

503 AUTH command used when not advertised exim4 - Outlook

I do keep on getting this error: 503 AUTH command used when not advertised I have seen this question : exim configuration: 503 AUTH command used when not advertised The difference is that i do not ...
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0answers
8 views

Cannot connect to smtp mail server [duplicate]

I have an installation of Postfix & Dovecot on a Centos 7 server. While being logged into the server via ssh I am able to use telnet and openssl to connect to localhost like openssl s_client ...
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0answers
25 views

Configure Postfix to send emails from my domain name

All my clients use gmail, but would like to use the domain name that I own, say domain.com to send from. I've already figured out how to forward emails that go to domain.com to its respective gmail ...
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1answer
64 views

Telnet: Unable to connect to remote host

Related Threads: SMTP server works, but telnet to port 25 does not Can't connect to SMTP server The problem I have a server running Debian 3.2.65-1 and i am having some problems to connect other ...
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1answer
34 views

reverse proxy for multiple SMTP / IMAP servers

Instead of giving our clients server name's like beta.example.com as IMAP / SMTP servers, we'd like to use smtp.example.com. We have a database of all domains / e-mail servers and corresponding mail ...
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1answer
17 views

STARTTLS sendmail handshake failures on SMTP and retries

I'd like to gracefully handle sendmail STARTTLS handshake failures. On outgoing mail, it would be best if there were an immediate retry without STARTTLS in the case of failure. On inbound mail, ...
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0answers
24 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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45 views

How to send an email with Powershell that doesn't end up in spam folder to Gmail?

I have various PowerShell scripts on Windows Server 2012 R2 that I like to notify me via email upon completion, so I setup a local SMTP server that is restricted to 127.0.0.1 only, and use this ...
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10 views

Firewalld not opening port 25? [duplicate]

Lookst like firewalld is not opening port 25. I tried adding the smtp service, and port 25 separately as well, yet, I am unable to telnet to the server. Any tips? [root@host ~]# firewall-cmd ...
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votes
2answers
52 views

How can I reject spam before reaching SMTP on Postfix

My server has started receiving thousands of attempts to use my mail server to send spam from dynamic.hinet.net. The attempts are always rejected, but it's non-stop. I'd like to block these attempts ...
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0answers
31 views

Using MX records for load balancing on *outgoing* email: bad practice?

I operate a Rails application (a Discourse forum) that needs to send out email. My sysadmin told me I shouldn't use a specific outgoing mailserver, but rather specify my domain and have my app lookup ...
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2answers
36 views

Can Mandrill route inbound email to webmail (like roundcube)

My main issue is I setup a small server, and my ISP blocks port 25. I've setup Mandrill as a relayhost on port 587 in postfix, so that solves my sending issue. I know Mandrill can be used to route ...
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1answer
38 views

SPF check failed

I am having trouble with failing to deliver mails with my setup. Server 1 - example.com + Direct Admin IP: 111.111.111.111, default domain (provided by hosting company: vps11111.company.com Server 2 ...
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1answer
22 views

How to choose a smarthost based on From: address in exim4 on Debian

I want to route emails with the From: .*@host1.com through smtp.server1.com and emails with the From: .*@host2.com through smtp.server2.com. For the moment, I have smarthost configured with ...
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votes
1answer
30 views

Add a second IP to SPF record, from an external SMTP server [closed]

I would like to add the IP of an external SMTP server to an existing SPF record, which is looks like this: "v=spf1 a mx ip4:185.6.139.6 a:frey.mailpool.1.netmask.hu a:frey.mailpool.2.netmask.hu ...
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votes
1answer
13 views

Exchange from field in iso format when ø character in name

I have setup a forward connector on Exchange (2010 SP2) named (f.e.) target.domain.no. The forward record points to a Windows Server SMTP Server (EMSERVER). Now I see in that emails that have the ø ...
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31 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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1answer
46 views

Can send email but can not receive email on Windows Server 2012 R2 with MailEnable

I am configuring a VPS on Windows Server 2012 R2 using MailEnable as email server. As the port 25 is blocked by ISP so I use port 587 instead. When configuring on email client Outlook or ...
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votes
1answer
85 views

Sendmail: “TLS verify=FAIL”, “554 5.1.8 : Sender address rejected: MX record not found”

Have been struggling for a day already and can't find solution. When try to send mails to some hosts: Jan 5 10:31:37 vps**** sm-mta[2192]: STARTTLS=client, relay=mail-x.*****.co.uk., ...
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votes
1answer
31 views

SMTP Server with dynamic / Static IP

I have 3 servers and 3 IP's. Server 1 - Static IP - 111.111.111.111 Server 2 - Static IP - 222.222.222.222 Server 3 - Dynamic IP - 333.333.333.333 Now Server 3 is always assigned the IP ...
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53 views

cant send to gmail. Remote host said: 421 4.7.0 Senders Guidelines

I have a SMTP account by hostgator. It has been working OK for a few years. in the last week all emails sent to gmail accounts are bounced with the following message: Could not deliver message to ...
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106 views

Postfix “Connection timed out”

I try to send a few emails, but postfix send only 3 emails every 10-20 min. After that postfix sends 3 emails, I get the error: "Connection timed out". mail.log: Jan 4 12:16:39 mail ...