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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How to configure synology NAS for SMTP server [closed]

first of all I have to admit that I'm a beginner in this topic. In fact this is my first post. I have a synology 213J that I want to configure as SMTP server. I discovered that I needed a domain in ...
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2answers
189 views

Postfix not sending mail :

I have postfix installed on my webserver and, since a couple of days, it seems that it cannot send mail anymore. All my messages are in postfix queue and I have each time the following message ...
2
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1answer
51 views

Service Closing transmission on OpenSSL [duplicate]

I am trying to send email through OpenSSL as below : Client > openssl s_client -crlf -connect smtp.mail.yahoo.com:465 SERVER > 220 smtp.mail.yahoo.com ESMTP ready Client > HELO localhost ...
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1answer
191 views

“Postfix SMTP server: errors from *” repeated automatic response

I'm attempting to setup a mail server with Postfix and Dovecot. It's not really working all that well, but there's something more urgent I'd like to get fixed first. I sent a few test e-mail ...
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2answers
51 views

How can I allow specific addresses to send email?

I have a network split into two parts - one for office and server computers, and one for computers that manage scientific instruments. The instrument computers are running on the vendor's patch ...
1
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1answer
73 views

SMTP Server will not send to connected VPN domain

I have a Windows 2012 web server that is connected to a company's VPN (vpn.company.com) to access network resources and needs to send emails to users of that company as well. When the web server is ...
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2answers
210 views

Setting up SPF records on dedicated server

I have a question in regards to SPF records in a dedicated hosting environment. I wish to set up an SPF record for my dedicated server, but I am not sure whether my understanding is correct. First ...
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2answers
427 views

Why is my email being rejected?

I am having problems sending an email from one email address to another on my domain. I am using a shared server. I use weather software which automatically constructs and sends the email message. I ...
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0answers
145 views

Virtual SMTP to send email through Exchange Server (via EWS)

We have a web application hosted by a third party that must send e-mail using an existing MS Exchange Server 2007 account in our premises. This application only connects to SMTP Servers. Our ...
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1answer
81 views

Overriding selected recipients using postfix

Is it possible to have some kind of regex match and replace, like it is possible for outgoing mails for incoming, too? I am already able to replace the from field for outgoings, by using the ...
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1answer
33 views

What is the maximum message size that SendMail can successfully receive and where would the bottlenecks be?

CentOS 5.x | SendMail 8.14 I'm curious - what is the largest message size that SendMail will successfully accept from an upstream source via SMTP? The tweaking config options page indicates that by ...
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1answer
1k views

Postfix/smtpd: Client host rejected: cannot find your hostname

I'm trying to set-up a mail server, using postfix and dovecot. Everything works fine, and I can connect in IMAP using Mozilla Thunderbird. But when I'm trying to send emails using the smtp server, I ...
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1answer
44 views

IPtables mail is not working though i allow smtp traffic

I'm working server Centos 6.5. I allowed incoming and outgoing traffic for SMTP as below though i'm unable to sent mail from server if iptables are switch on. My IPtables files rules are as below ...
0
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1answer
128 views

cPanel Change SMTP send port [closed]

Our ISP blocks outbound port 25 (annoying) and we are currently paying for a relay service. One of our clients on the server is running a high traffic website and pretty much everyone who goes on the ...
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4answers
169 views

How can I secure postfix so my ISP won't block it?

Our dev server is a CentOS LAMP system for developing web sites. We want PHP to send email. The server doesn't need to receive email or anything else, literally just send email to our developers. I ...
0
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1answer
86 views

Fail to relay email with Postfix

I want to relay mail to local SMTP to mandrillapp, with the /etc/postfix/main.cf smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu) biff = no append_dot_mydomain = no smtp_sasl_auth_enable = yes ...
2
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0answers
175 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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0answers
30 views

Postfix tries to deliver forever

I have a postfix mailserver on LAN which is only used to send email alerts to internal domain names. It does not have any route to the internet, nor does it have a DNS setup. Now after couple of ...
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2answers
66 views

Do I need SMTP when using Postfix/Dovecot? [closed]

I have setup Postfix and Dovecot. Microsoft outlook tells me it cannot find the SMTP server. I thought dovecot would handle all the deliveries? Do I need to allow postfix to listen to external ...
0
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0answers
62 views

migrating to new server, would like to keep sending email from existing server

Hello I'm in the process of moving my site to a new host (ie new IP). I run a social site that sends a large volume of (valid) email, and I have built up a good sending reputation with my current IP ...
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0answers
71 views

force upstream smtp outbound through proxy

Upon inspection of emails sent outbound to external domains, the backend is revealed as being the true sender, rather than the proxy itself. When sending within the domain, from local user to another, ...
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1answer
38 views

Should I block the other SMTP ports as well to block outgoing mail?

I have blocked outgoing port 25 to prevent spam being sent from my servers. However, I'm not very familiar with SMTP and I have heard that ports such as 465 and 587 can also be used to send mail, but ...
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0answers
42 views

Tripwire unable to send mail

I'm installing Tripwire Enterprise Console (Server) onto a windows server that happens to be an SMTP forwarder. I proceed through the steps to install TEC and it completes not reporting any errors. ...
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1answer
166 views

How can I disable sending mail through postfix smtp with out auth

I just setup a mail server with postfix 2.6.6 and dovecot. I have the auth related config in main.cf like below: smtpd_tls_cert_file=/etc/httpd/ssl/mail.crt ...
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1answer
274 views

Configure Citadel to be Used For sending email using smtp

Sorry for this foolish question, but I have less knowldge about servers. So bear with me! I have configured Citadel as directed in linode documentation and can login using the front-end for accessing ...
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1answer
120 views

Sending mail from PHP gives Unrouteable address

I have a Debian server running PHP and Exim4 (among other things of course). The PHP application is sending 1000s of emails every day all of which work fine, however I now have a new customer and my ...
0
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1answer
143 views

Using IIS smtp for incoming and outgoing and use hMailserver for mail accounts

I have installed hMailServer in one machine and IIS STMP in another machine. Even though hMailSever itself is a SMTP server. I can't avoid this because the IIS SMTP server has some hooks which which ...
2
votes
1answer
144 views

What does an empty AUTH EHLO SMTP response mean with MS Exchange?

I'm a programmer, not a sys-admin, but my customer's sys-admins are not being helpful and after much googling I still can't find the answer to this. My Java application gets the following response ...
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2answers
115 views

If I use postfix for mail relay, so is myhostname / mydestination important?

I use postfix to relay mail to 3rd party SMTP and never sent out email directly, and of course I never receive email. So If I set myhostname / mydestination to sth like fake.mydomain.com, which ...
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1answer
83 views

Email sent from my new server, being suspended by SMTP because “weird” hostname?

I have some problems sending emails from my server: I've been banned/suspended for abuse (IP blocked) by the SMTP server. This happens only on my new virtual server. Right to the question: is my new ...
0
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0answers
48 views

SMTP - Apache SOLR - Localhost to Server

I'm developing a single page application (ajax-php-mysql) using XAMPP (localhost). The app needs to be able to send out quite a few emails per day, not anything crazy like 100,000 but I do suspect it ...
0
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3answers
392 views

Is blocking SMTP ports prevent server from sending emails?

I have a Centos server with cPanel on it. Yesterday, some hackers had successfully connected to my smpt server and sent thousand of emails from it. What I want to do is blocking every ports except ...
0
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1answer
183 views

smtp relay attack on our mail server (not an open relay server)

Help, We put our Exchange Server (10.0.0.125) behind a SMTP Proxy server (Xeams if you have heard of it), however recently our client complaints we replies their email too late - and we found ...
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1answer
79 views

Random synchronization error on SMTP server

We can send mails across the network from 1 server to another via a centralized smtp server. However, the we get a synchronization error on the server randomly. So for example if we send a simple ...
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1answer
96 views

SMTPD restrictions

i'm looking for a bit of advice on Postfix restrictions configuration. I'm looking for a balanced configuration which properly rejects spam and unauthorized access retries. Lately, i've been reading ...
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votes
2answers
315 views

Google blocks authentication attempts by my machine to transfer outgoing mails [closed]

I am using gmail as SMTP server (via ssmtp mail transfer agent in Ubuntu 12.04) for sending outgoing mails from my server. But the problem is that Google often blocks authentication attempts by my ...
1
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1answer
81 views

Postfix does not reject wrong client and HELO name

I have a postfix server configured with reject_unknown_client_hostname and reject_unknown_helo_hostname. Regardless the server accepts non sasl_authenticated connections from clients and HELO names ...
0
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1answer
89 views

SMTP Connection disconnecting after “STARTTLS”

We're having issues with our mail server. Basically some emails from external networks are not being accepted by the mailserver. After some debugging using telnet and looking through the logfiles, it ...
0
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1answer
101 views

change ehlo name of Amavis

Server: Ubuntu 12.04 64 bit Setup Postfix + Dovecot + Amavis with Mysql for Virtual domains. I have configured the postfix mailserver successfully. However when I test the Email with mail-tester.com, ...
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2answers
251 views

How to stop or prevent Postfix / smtpd / Sasl brute forcing

There are numerous attempts to connect to my mail server in order to send mail either unauthenticated or to guess username and password to, I suppose, accomplish the same. Should I fight against ...
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1answer
30 views

What is the correct way to get an NDR to be sent when a bounce back occurs?

I have a user who developed a WebApp that sends SMTP messages. Users are able to reply to the message using a MUA (outlook, whatever) but there is no NDR if the user doesn't exist. I suspect that ...
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0answers
616 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 ...
2
votes
1answer
72 views

How easy is it to sniff the SMTP port of webserver to capture mails

I've got a very basic question that I don't know the answer for. Our company owns a webserver that runs multiple websites and works as a mail server for these websites as well (e.g. to send contact ...
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votes
1answer
78 views

SBS 2003; Exchange 2003 can't receive mails without SMTP connection but without POP3 connector [closed]

i hope you can help. I'm losing my mind. I'm not a specialist in SBS but i have a huge problem. I wanted to replace the mircosoft pop3-connector with popcon because i was told that several mails ...
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vote
2answers
85 views

Correct FQDN Setting?

I can see from SMTP logs that some mail is being rejected OutboundConnectionResponse SMTPSVC1 Sxxx - 25 - - 504+:+Helo+command+rejected:+need+fully-qualified+hostname 0 0 69 0 47 SMTP In ...
0
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1answer
88 views

Where does e-mail header “Received: from…” come from? [closed]

I sent myself an e-mail from my server to my gmail account, here is one of the headers (partially redacted): Received: from cpvds3xx.xxx.com (dev1.xxx.com. [209.51.132.xxx]) by mx.google.com ...
6
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2answers
467 views

Why is email being delivered normally despite an SPF “hardfail”?

I'm trying to figure out why forged email is being delivered to major email providers (gmail.com, outlook.com) even though email is marked with an SPF hardfail. The email is also delivered to ...
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1answer
237 views

hMail delivery queue full with unsuccesfull spam

Since a day or two the mail delivery queue of the hMailServer is exploding because someone is trying to send spam via this server. Though the e-mails aren't successfully sent it fills up the mail ...
0
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1answer
51 views

Is extra “Received by” in mail headers bad and can I remove it?

I use our own VPS web and mail server to send out a newsletter regularly to 50,000 addresses. I am trying to improve deliverability and was looking through some of the thousands of bounce emails. One ...
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1answer
32 views

Scanning server results in warning about STARTTLS [closed]

After scanning our webserver, I've got this message: The remote SMTP service, support the user of the 'STARTTLS' command to switch from a plaintext to an encrypted communications channel. As I ...