Questions tagged [smtp]

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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702 views

MX priority server behaviour

This is a question about MX procotol priority. If I have two server as MX with different priority: MX 10 serverA MX 20 serverB Is this guarantee by the protocol that the MX 10 is the prefered? Can ...
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3answers
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In the mail header, what does the “received from” ip refer to?

I noticed that some mail header contact a field called received : from and it contains an ip address. Does this address refer to the sender machine even if he is using a web interface or to the ...
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1answer
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How can I configure Postfix to ignore relayhost for some domains?

Is there a way in Postfix to ignore the relayhost? I have something like relayhost = [smtp.domain.net]:587 Now for a certain domain I don't want to send it out to that relay but want it to just ...
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5answers
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Recommendations for SMTP services for massive mailing [closed]

What is the recommendations for SMTP services for massive mailing? Let me clarify, most of the free SMTP services (Gmail, Yahoo, Hotmail, etc...) has limits about the amount of messages you can send ...
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6answers
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fake “from” field in an email

How can I manipulate the "from" field in an email and make the "to" user see something different then the actual. Example: really from From: TStamper@yahoo.com but they see From: Tremayne "...
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3answers
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Can't get SASL auxprop/sasldb working with postfix/Ubuntu 12.04

I have an Ubuntu 8.04LTS system running Postfix 2.5.1. On that system SMTP AUTH runs fine. The contents of /etc/postfix/sasl/smtpd.conf are: pwcheck_method: auxprop auxprop_plugin: sasldb mech_list: ...
9
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4answers
26k views

Fastest way to allow sendmail relay through smarthost?

I only want sendmail to relay through my ISP's smtp server, nothing else. How do i set it up?
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2answers
5k 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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5answers
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How important are PTR records for Email Servers?

Does anyone know of any studies done to show how much email will be rejected if there is not ptr record for the SMTP banner name of an email server? Are reverse checks always done when enabled, or ...
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2answers
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In postfix, how to enforce tls + auth over 587 while leaving tls optional for 25

I would like to host mail services for some domains. I have succesfully setup postfix to consult sql for those virtual domains. What I would like to do is: For connections on 25: Deny relaying (...
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3answers
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mail loops back to myself | postfix

Hi I have an issue with bounced mail it does not happen all the time but at the same time is very frequent. Most of the time if I send an email to an address that does not exist then i get a bounce ...
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1answer
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Postfix reject_unknown_reverse_client_hostname: replace default unknown_client_reject_code (450) to 550. Why/When I should not?

In the daily battle against SPAM, there have been several times when I've been tempted to heavily enforce DNS requirements from clients connecting from the wild Internet. In detail, I would have ...
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1answer
2k views

Should I listen for SMTP on both 25 and 587?

I was setting up haraka as our mailing server, and for outbound email, it suggests moving to port 587 for SMTPS auth support. However, I'm unsure if I should be running 2 instances of haraka on both ...
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3answers
26k views

smtp remote host responds “550 Sender verify failed”

A server I'm taking care of uses qmail for MTA. I can send and receive to almost every domain except one or two that give the following error, or something very similar: 550-Verification failed for &...
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3answers
4k views

Exclamation marks being inserted into Emails at approx 1000 character mark

Have a .NET program that uses the System.Net.Main namespace to send an email via SMTP. Its on a customers site so from there it will go via a (series of?) SMTP relay servers before it reaches its ...
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3answers
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554 - Sending MTA’s poor reputation

I am running an email server on 77.245.64.44 and have recently started to have problems with remote delivery of emails sent using this server. Only about 5% of recipients are rejecting the emails, but ...
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3answers
198 views

Name one good reason for immediately failing on a SMTP 4xx code

I'm really curious about this. The question (highlighed in bold): Can someone name ONE GOOD REASON to have their email server permanently set up to auto-fail/immediate-fail on 4xx codes? Because ...
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1answer
1k 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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2answers
604 views

How can I use wildcards for sendmail TLS_Rcpt?

sendmail lets one place restrictions on TLS conversations. I want to check that messages sent to example.com are sent to a server that has a *.messagelabs.com certificate. I want to protect against ...
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6answers
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Under what circumstances (if any) should an MX record point to localhost?

I'm thinking that there's absolutely no reason or justification for this, but before I open my mouth and get some admin in deep kimchi, I thought I should ask. Is there any circumstance in which an ...
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2answers
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Can I have an MX record for a 3rd level domain?

I have mail working for continuumconcepts.com right now. My mx records point to my assigned google postini servers. Works great. I have another server out in the wild that is completely disconnected ...
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4answers
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How does a Reverse DNS lookup work with regards to spam filters?

I have heard that most spam filters use a reverse DNS lookup on the originating IP address of the sending SMTP server (or something like that) as part of the verification process. I want to make sure ...
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2answers
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Is setting up my own SMTP server to send email a waste of time with regards to deliverability?

I have a dedicated host serving a few domains I manage. I host my own email and IMAP server. The server is at buildoneforme.com with IP address 144.76.81.247. I think reverse DNS is working: $ host ...
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2answers
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Custom headers in Email lost?

I have some questions about custom mail headers Does anybody know of any mailserver which deletes proprietary/custom headers when being transmitted to its destination? Is there a header you can set ...
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4answers
676 views

Steps to take to improve email deliverability [duplicate]

Successfully delivering email to my clients is a pretty high priority at my company. We are of course fully opt-in, paid clients, no possibility of spam, the whole thing. The information we email is ...
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3answers
12k views

IIS6 Virtual SMTP server isn't coming back up automatically after a system restart

I've got a virtual server running Win2008 RC2. I've set up IIS6 with a virtual SMTP server on it to be the mail provider for the websites I'm hosting there. It all works great, but if for some reason ...
8
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1answer
10k views

Mail queue retry interval practices

I'm configuring a custom made mail queue. The thing is there can be errors sending mail. Normally, one won't know the reason why the mail didn't reach it's destination. So the most simplistic solution ...
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2answers
617 views

Dealing with SMTP invalid command attack

One of our semi-busy mail servers (sendmail) has had a lot of inbound connections over the past few days from hosts that are issuing garbage commands. In the past two days: incoming smtp ...
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1answer
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Cisco FWSM -> ASA upgrade broke our mail server

We send mail with unicode asian characters to our mail server on the other side of our WAN... immediately after upgrading from a FWSM running 2.3(2) to an ASA5550 running 8.2(5), we saw failures on ...
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1answer
3k views

Windows Server 2012: Cannot install SMTP-Server, system always requires restart

I'm not able to install the "SMTP-Server" feature on a Windows 2012 server. The installation process always fails with a "restart required" message. After the restart and (re)starting the SMTP-Server ...
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7answers
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Very simple SMTP server for Ubuntu wanted

I'm looking for a very simple, lightweight SMTP server to run on an Ubuntu 9.04 VPS. The only functionality I need is to support the PHP mail command; <?php mail('caffeinated@example.com', 'My ...
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6answers
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Recommended personal mail server setup [closed]

I've been using GNU/Linux for servers, mostly Debian. I am thinking of keeping my personal email on a centralized server. I have some GMail accounts, and a few from different domains from several web ...
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2answers
5k views

Display a TLS icon for messages that are TLS secured (Outlook)

One of my colleagues at a large financial institution has customised Lotus Notes to show a TLS icon for messages that are TLS secured. I'm interested in imitating this feature in Outlook, and believe ...
7
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4answers
16k views

Reject incoming emails that use your own domain as sender

It would be nice to reject incoming emails which use one of my virtual domains as sender address while not being a legitimate user of mine. I know that I can reject incoming emails which use an ...
7
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6answers
21k views

How can I set up sendmail to forward all mail to an external MTA?

We have multiple applications that currently talk SMTP to an external MTA. The emails have arbitrary destination domains (they're emails to be sent to our users), but all from the same internal domain ...
7
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1answer
17k views

Why would an SMTP client send a RSET (Reset) command?

I’m trying to understand how exactly an email is processed by Postfix – and some of the finer details of SMTP mail transactions. My short-term goal is to debug a proprietary (binary, closed source) ...
7
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3answers
515 views

Is it a good idea to reduce the give-up time for e-mail delivery?

We run an e-mail server for a few customers, and we've recently run into a bit of a conundrum. We had a user who sent an e-mail to an incorrect e-mail address. The incorrectly specified domain ...
7
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4answers
23k views

Disable SMTP AUTH on Port 25

Due to PCI-DSS, we are required to disable plaintext authentication. We've achieved this by encapsulating communications between our mail server and clients with TLS on port 465. The problem lies in ...
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3answers
5k 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 ...
7
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3answers
1k views

Will mailing lists “break” if SPF is too restrictive?

I have recently configured my own mail server (Linux-based postfix + dovecot scenario). This is just for personal use - I have no bulk mail going out, no automatically generated mail outbound from the ...
7
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3answers
608 views

(How) do you run “functional” tests on your services automatically?

Consider a simple FreeBSD machine running an SMTP server - how can I automatically verify that it's doing the right thing (e.g. accept incoming SMTP connections for certain recipients, and drop the ...
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2answers
360 views

What is the difference between 3-digit and dotted SMTP error codes?

When looking up SMTP error codes, I sometimes see "550", or "5.5.0". And sometimes the number in the dotted code is different. I found the numeric codes defined in RFC 821 and the dotted codes in RFC ...
7
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1answer
31k views

How to configure sendmail to send email via GMail (smtp.gmail.com), using port 465 or 587?

I have configures sendmail to send email via my GMail (Google Mail) account, i.e. via smtp.gmail.com, by editing /etc/mail/sendmail.mc and regenerating sendmail.cf: -dnl define(`SMART_HOST',`smtp....
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5answers
6k views

Is the IIS SMTP Server good enough for a production server?

I was planning to use the SMTP server that comes with IIS7 (for a website) but then I came across this link and started to get worried (read the accepted solution), on the other hand I have a limited ...
7
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2answers
7k views

How to add DKIM feature to the IIS 7.5 - Windows Server 2008 - DomainKeys Identified Mail

How to add DKIM feature to the IIS 7.5 - Windows Server 2008 DomainKeys Identified Mail
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1answer
7k views

Windows Server 2008 SMTP Server is not writing to log file

I use Windows Server 2008 as my development operating system. I have been able to test that the SMTP Server on the machine can successfully send emails (I receive them in my inbox) but the log file ...
7
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2answers
4k views

Amazon SES vs EC2 Smtp server

We have an existing smtp environment setup in an EC2 instance which is used to send Transactional emails like password reset. Now we have a requirement to send System emails to a large user base in ...
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2answers
2k views

Expose IIS SMTP Pickup folder as a file share - bad idea?

Environment: IIS Web Farm 5 servers Windows Server 2008 R2 IIS 7.5 ASP.NET 3.5 and 4.0 web application Our web app, like many, needs to send mail. Send only, no receiving. In the past, we've ...
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4answers
22k views

Mailbox unavailable, client does not have permissions to send as this sender - only the first time

Our users can send emails from our ASP.NET Web application on the click of a button. In our testing environment, there is a strange thing going on. The first time the application tries to send the ...
6
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6answers
12k views

postfix fails to send mail with “fatal: unknown service: smtp/tcp”

I have installed postfix, and when I tried to send a mail to gmail it told me that it has been sent, but when I checked my inbox in Gmail I didn't saw it. This is how the connection looked like: $ ...