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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SPF redirect modifier

The SPF record for domain replace the current record. The macro-expanded domain is also substituted for the current-domain in those look-ups. Examples: In the following example, the ...
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2answers
45 views

Postfix Catchall - Avoid Spam

I've 2 accounts on my CentOS server configured with catchall email accounts. Lately I've been receiving bounced emails with virus that were supposedly sent from my server account, Ex: somestragename@...
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25 views

Sendmail not forwarding mail for domains in /etc/mail/local-domain-hosts

First off, I have been using sendmail for about a week, and have a semi-working instance. This issue very well may be something simple/overlooked. I have an AMI server that is running sendmail and ...
7
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1answer
113 views

Trying to setup mail server, can't get ports (25, 587) to work

I've searched everywhere and I'm really struggling with this one. I think I've tried just about everything. Background info VPS with CentOS 6.7 Postfix 2.6.6 dovecot, amavis, mysql, fail2ban I've ...
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0answers
43 views

SMTP IIS Relay - attachments are encoded in email body

Server 2008 R2, MS IIS build 7.5 being used as an outgoing SMTP relay only. Session/message limits and attachment limits set to 500 MB per attachment and session. Attachment is between 10-20 KB. ...
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0answers
98 views

How to allow authenticated User to relay on a Cisco ESA C170 (iron port)

I'am trying to configure my ESA C170 and all works as expected. But now I want to add support for relay function for authed external user. I add a SMTP Auth Profile against LDAP that works. Next Step ...
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1answer
60 views

Mail Server allow sending spam to own domain

I am having trouble configuring my mail server (Dovecot and Postfix). The problem is that someone can send spam mails to my address from my own mail server. The server is not open-relay but it seems ...
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9 views

courier-authlib not connecting on Gentoo

I may have 2 issues, or miss reading one. logs: May 15 11:17:17 r2d2 authdaemond[26904]: Installation complete: authpipe May 15 11:17:30 r2d2 postfix/smtpd[26986]: sql auxprop plugin using mysql ...
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1answer
42 views

What exactly does “probable open proxy: command=POST” mean in sendmail logs?

I noticed the following in my sendmail logs: May 11 11:11:16 foobox sendmail[21111]: uADEFHG21111: [1.1.1.1]: probable open proxy: command=POST http://foo2.example.com May 11 11:11:16 foobox ...
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1answer
37 views

How can I easily setup a SMTP reverse proxy from EC2 to SES?

How can I easily setup a SMTP reverse proxy from EC2 to SES without revealing SES the original SMTP Client IP?
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1answer
46 views

Mutt suddenly stopped sending emails with attachments via Postfix

Issue arose when an attachment froze at the send stage (after uploading fine) in mutt 1.5.24. I updated to mutt 1.6.1, same compile flags, but still didn't send. Tested in Thunderbird (icedove) and it ...
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1answer
82 views

How to set up an SMTP Relay Server

I have 2 servers (X and Y) and an SMTP server for sending emails. X needs to send an email using the SMTP server, however it cannot resolve the host for the SMTP server. This is inevitable and I need ...
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1answer
62 views

Who's blocked access to my SMTP port? [closed]

I have a very small scale personal mail server than I run on a VPS. Yesterday I migrated this, and changed the DNS records with the registrar (godaddy). Because of some limitations on the new host OS,...
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2answers
74 views

Binding domain and SMTP server on a foreign server

I have a trouble with my server setup, I'm trying to bind both IP domain + his SMTP server on the same external server. However mxtoolbox still give me the same error : "Reverse DNS is not a valid ...
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1answer
34 views

Why does nginx need an auth_http entry for smtp reverse-proxy?

I'm an apache user normally, but I need to start using nginx as a reverse proxy for smtp (postfix). I've seen tens of examples online. Like this and this. All of them have an auth_http entry, which I ...
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1answer
149 views

Postfix NOQUEUE: reject: RCPT from unknown

I built a web based application but when it is trying to send an e-mail it fails. Postfix logs the following in it's mail.log: postfix/smtpd[22261]: warning: hostname srv.eastinc.nl does not ...
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3answers
108 views

Is it possible to reject certain emails in procmail? [In SMTP session rejects based on email content]

Let's assume a typical setup where procmail is called from sendmail to filter incoming emails into correct mailboxes. Is that done while the incoming SMTP connection to sendmail is still active or is ...
3
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1answer
67 views

Logwatch is not respecting MailFrom

I've gone through today to setup Logwatch on my server and have installed this all successfully. I've followed this guide on Digital Ocean and set the MailFrom parameter to: MailFrom = mailer@...
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0answers
9 views

What's a reproductable way to set up a Linux server for sending e-mails but no spam? [duplicate]

I've created a software that has to be installed onto a Linux server and from time to time it has to send a notification email. So, for people who want to use my software, I've created a bash script ...
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2answers
82 views

Testing an SMTP server with SSL?

I want to be sure a SSL/TLS connection is really being made to my SMTP Server on port 465. (The Server is running on Ubuntu 14.04) Using:- openssl s_client -connect example.co.uk:465 I get ...
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0answers
26 views

SMTP Mail delivery failed for URIBL query refused

I'm experiencing some trouble with a single recipient because his mail server refuse my email. This is the error reply: SMTP error from remote mail server after RCPT TO:<xxxx@xxx.xxx>: 554 5.7....
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2answers
45 views

Should a mail server receive mail at the hostname or just the domain?

When configuring a mail server, should it be setup to receive mail at the hostname or just the domain? For example, if the hostname of the mail server is sub.domain.tld, should mail from anywhere be ...
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0answers
22 views

Which wireshark output format aligns closest with actual SMTP data?

I have a packet capture of a SMTP session (containing an email with international characters). I'd like to extract the message data from that and try reproducing an issue. When I follow the TCP ...
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48 views

How to encrypt emails sent from Windows Server 2012 SMTP IIS 6.0

I'm running an SMTP server through IIS 6.0 on my Windows 2012 Server, and would like to make delivery of emails to be encrypted. I have attached an SSL certificate to the server and set Require TLS ...
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2answers
110 views

Secure Email Settings for Email Clients & for PHPMailer

I'm trying to work out how to make my outgoing/incoming email's as secure as I can possibly make them. First of all, my domain has Wildcard OV SSL Certificates, I have copies of the .csr, .crt and ....
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2answers
30 views

Telnet windows 2008 vs 2003

I have a mail server using powermta on a windows 2003 server (legacy). If I telnet into that server to test smtp connectivity, it works from other 2003 servers and from my dev machine running windows ...
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3answers
91 views

Setting up an email proxy server?

So i have 4 application servers and each one directly connects to an SMTP server to send out the emails. What I want is to have something in the middle that my servers connect through instead, and ...
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1answer
126 views

Number of issues with postfix, DKIM, and mail getting rejected or bulked

I'm having a number of issues with Postfix and mail sent being rejected or put in the spam/junk folder. I am trying to send emails on behalf of a number of my customers. I've got a postfix server set ...
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1answer
69 views

Exchange server 2016 Content Filtering

I have setup an exchange server on premise with at SMTP Relay on our VPS. It works very well, unfortunately I’m a little confused as to where I setup the various permissions for SPAM. All my incoming ...
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2answers
87 views

postfix allow localhost only local users

I have a little problem. I am offering some clients access to my server in order to execute own scripts (of course in their own chroot environment, etc...). The problem which occured today: Some ...
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2answers
78 views

IIS Smtp server cannot send to hotmail,outlook, etc addresses

I have a SMTP server on a Windows server 2008 R2. It can send messages to all other domains except the ones hosted at Microsoft (hotmail.com,outlook.com, etc). The email messages it cannot send remain ...
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1answer
87 views

Sending mails from Gmail through my VPS (postfix, dovecot, postfixadmin)

This problem has been bugging me for a long time now and i want it to be fixed. On my VPS I have set up Postfix working correctly with postfixadmin and dovecot. (I can send (by terminal) and receive ...
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1answer
62 views

exim4 issues sending mail to gmail

I am trying to send automated emails from my server to my gmail account, so that I can get important notices like when my webserver is not responding, or just some daily statistics. As email sending ...
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2answers
55 views

How do I enable recipient verification in Exchange?

My problem basically boils down to this: Exchange (2016) is accepting mail for non-existent addresses and then later sending out DSNs (delivery status notification) to notify the sender of failure. I ...
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1answer
109 views

How to configure postfix with ufw so that my web server can send email but it doesn't act as an open relay?

According to this guide: It is important to secure your server and make sure that Postfix is not configured as an open relay. It links to another guide which suggests using UFW as a firewall. I'...
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39 views

Nullmailer: Unable to resolve host

After installing Ubuntu on my VPS the hostname was Ubuntu-1404-trusty-64-minimal. I changed it to hetzner-backup-1 and rebooted. What I did: I did nano /etc/hosts and added: 127.0.0.1 localhost....
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1answer
37 views

Postfix/LMTP rewriting username to number 1

I have a frustrating issue with my mail server and i am confused as which part of the configuration is concerned, please note that both postfix and dovecot are configured to fetch configuration from ...
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2answers
1k views

Is an IPv6-only MTA possible yet?

Has anyone had tried to run an IPv6-only SMTP engine? Pretty much everybody with any sense has IPv6 configured for major front-end servers. I was curious if anyone had tried to run an IPv6-only MTA ...
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1answer
40 views

Outgoing emails not being encrypted

I am using postfix to send email. I have mysql set up to manage domains, accounts, and aliases. I have 3 domains set up. One domain is the primary domain and when sending emails to gmail accounts ...
0
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1answer
61 views

IIS mail server relay mails stuck in queue due to DNS?

Recently our internal SMTP relay server stopped working - or rather, stopped sending emails. It responds to send mail requests, a simple TELNET session shows no errors, but all messages get stuck in ...
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1answer
114 views

Is it possible to send emails to a gmail address WITHOUT using GMail as a relay server?

I've been fighting all day trying to properly configure Postfix to get the emails delivered to GMail addresses I finally got it by using GMail's SMTP as a relay server, sadly that server overrides ...
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votes
1answer
49 views

Mail server with different IP than webserver - getting 554 error

I have a webshop running on a Digital Ocean droplet, while the email inbox for the same domain is running on a different VPS. All of the sudden some of the emails sent by the webshop are being ...
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2answers
75 views

Port decisions for email setup in 2016 (Ubuntu)

I have a new Ubuntu 14.04 LAMP server with the UFW firewall setup on DigitalOcean. My goal is to add email for use on my phone(iPhone) and laptop(via Roundcube). There is a lot of old information ...
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1answer
30 views

OpenVPN block SMTP Access Server completely

I've tried almost all iptables rules to block smtp on openvpn server but still clients clients can access remote smtp servers on port 25. I'm using openvpn access server. It's creating two interfaces ...
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1answer
33 views

Web App Error After Installing Java on Centos Server

Good day. My web app is programmed in jsp, using some of jQuery and javascript, is on a server with Centos 6.4, the app run its own java 1.7.0 - tomcat 8.0.21 and between its functions, uses javax....
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23 views

Workaround 554 5.7.1 Error

I've posted this question some days ago, 554 5.7.1 You are not allowed to connect. sending from postfix Based on the answer I've sent some emails to the admin of the other email server, ...
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1answer
52 views

Javamail using Exchange as relay

I have to fix an "unable to relay". The java server has to send emails to the internet. The java server and the exchange server are in the same network. How I configure properly a receive connector in ...
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0answers
84 views

GitLab on CentOS 7 (not sending email) after applying recommendations

GitLab not sending mails and GitLab email notifications not sending have been attempted with no success. I have an GIT with GitLab as a web management setup. However, invitation/confirmation ...
0
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1answer
76 views

Postfix mail server refuses connections from outside mail servers

I have a Postfix server with SMTP listening on port 587 which cannot be reached by outside mail servers like Gmail and hence I receive this Mail Delivery Failure when sending an email from GMail to ...
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2answers
125 views

Exim: Force email auth for users of local domains

I'm configuring exim4 for virtual users with dovecot and postgresql and I got a problem I cannot resolve, the situation is this: I need that when a 'localdomain' user tries to send a email to another ...