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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SMTP daemon on alternate port to capture all messages to single Dovecot mailbox

There's several answers on here about how to configure postfix to redirect all messages to a single mailbox, for development/testing of mail scripts. I'm looking for a variation on this where I open ...
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2answers
107 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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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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1answer
10 views

What does sendmail need to specifically see in order to determine if a remote MTA supports 8-bit MIME transport?

I'm troubleshooting an intermittent issue where some international characters appear to be malformed after going through sendmail. I recently came across this article which describes the F=7 ...
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1answer
160 views

Is there a way to “replay” a packet capture of a smtp session for the purpose of debugging?

I'm troubleshooting a smtp issue involving character-set encoding and it's extremely difficult to involve the end user. I have a packet capture of an incoming smtp session that results in problematic ...
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2answers
63 views

How to fix 'Relay Access Denied'

I'm trying to setup postfix as MTA on a AWS EC2 instance. I want to use this as mailserver for my domains and want to use it along with Outlook/Thunderbird. I've never setup postfix before, therefore ...
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1answer
48 views

Postfix use outgoing IP based on incoming IP used

I am using Digital Ocean's Floating IPs on my mail server. So I have two publicly available IPs that the server can use, and I would like to use whichever IP was used to reach the Postfix server as ...
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1answer
45 views

Configure sendmail to relay on an smtp server

I'm using an ubuntu distribution. And I installed the sendmail with apt, and edited the /etc/mail/sendmail.mc, and added the lines define(`SMART_HOST', `ssl0.ovh.net') FEATURE(`authinfo') before ...
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91 views

Using Amazon SES to send mails to specific domains in Zimbra

We are managing a Zimbra mail server Community edition. Since the IP Address reputation of our ISP is a bit poor, select domains (mail servers) are either blocking our emails which is resulting in ...
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2answers
307 views

How to setup postfix to check SPF record only for domains that i want to check

I have working postfix server. It configured with amavis and uses pretty good SMTP headers control. But sometimes my users receive spam from spammers with well known mail service providers addresses. ...
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60 views

Spam sent from my dedicated server Centos/Postfix, no idea on how to block people from connecting

I've been reading a lot of topics here for the last 2 hours, made some change and yet I'm not sure how things happened and if things are fixed. First, this morning, I received an email from OVH, ...
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1answer
234 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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43 views

MessageLabs Blocking Email but Not Our Provider

My coworker and I am at a loss here. MessageLabs is blacking our client's emails from sending. However, MessageLabs isn't our anti-spam provider anymore. I checked SonicWALL to see if they're still ...
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1answer
27 views

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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1answer
33 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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22 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 ...
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1answer
112 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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1answer
684 views

How to add allowed relay IPs for Windows SMTP using command line or script

I have a long list of IP addresses I need to add as allowed relays to the built-in SMTP service on Windows Server 2008 R2 (IIS 7.5, but SMTP uses the old IIS 6.0 manager) I know how to add allowed ...
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42 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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89 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
59 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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1answer
6k views

Exchange 2010 SP3: 4.3.1 Insufficient system resources

We have Office 365 with a hybrid deployment. Our on-premise server is relaying email directly out to the web (not via EOP). domain-a.com is an accepted domain on our on-premise server; domain-b.com is ...
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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
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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4answers
22k views

SMTP don't work when try to send mail from mail client

Mail server works fine when send mail from server, but when I use some mail client it not work. I found this in logs: Jul 12 19:45:04 tvsite postfix/smtpd[3356]: warning: hostname adsl-bb29-l44 does ...
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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
19k views

Postfix “timed out while sending message body” to “Microsoft ESMTP MAIL Service”

For some reason we cannot send larger email to one of our customers. Small emails are fine, but even a message with a 1MB attachment fails to deliver for several hours - Postfix logs keep filling with ...
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1answer
79 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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138 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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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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2answers
73 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
136 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
106 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 ...
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445 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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1answer
65 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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2answers
77 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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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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25 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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1answer
3k views

Postfix on Ubuntu tried everything, won't send emails

I'm trying to get postfix set-up on Ubuntu 13.04 but no luck so far. I found a few answers here on ServerFault that didn't work. I re-installed a bunch of times, nothing. This is my first time dealing ...
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3answers
84 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
125 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
83 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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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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47 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
29 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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2answers
76 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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2answers
205 views

Zimbra (postfix) receives email from “my domain” but from external unknown server

I've installed a Zimbra 8.0.7, recently the server have become to deliver emails from accounts that belong to my domain ("example.com") but this mails come from external smtps, for example: 1. the ...
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1answer
67 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 ...