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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42
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4answers
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Is greylisting still an efficient method for preventing spam?

I've used greylisting on my servers for many years, but I don't know how effective it is nowadays. Is it still good for fighting spam in 2012? Or is the typical spammer MTA capable of resending ...
33
votes
1answer
56k views

What ports to open for mail server?

I have just finished setting up a Postfix mail server on a linux (ubuntu) platform. I have it sending and receiving email and it is not an open relay. It also supports secure smtp and imap. Now this ...
33
votes
5answers
248k views

How to correct Postfix' 'Relay Access Denied'?

This morning, in order to correct a problem with a name mismatch in the security certificate, I followed the recommended steps from How to fix mail server SSL?, but now, when attempting to send an ...
29
votes
7answers
71k views

SMTP server on Windows 7

Is it possible to install the SMTP server that you can install in Windows Server 2008 in Windows 7? Or something similar? I'm developing an application that will make use of it and I want to be able ...
26
votes
9answers
20k views

How to setup a fake SMTP server to catch all mails?

I'm looking for an smtp service that essentially obeys the RFC, except rather than sending mail it simply logs to a file [date] sent mail to <address> Or whatever. I can bash this together ...
22
votes
3answers
41k views

What replaces IIS SMTP server in Windows Server 2012

I have read the notes here http://technet.microsoft.com/en-us/library/hh831568.aspx regarding deprecated and removed features in Windows 2012 and it says that SMTP is deprecated. I assume this is ...
21
votes
6answers
22k views

Do SPF Records For Primary Domain apply to subdomains?

I have a quick question regarding SPF records: Do they need to be present for all subdomains? Lets say that I have a TXT record with SPF info for domain.com Let's also say that I have a seperate ...
18
votes
4answers
74k views

Fixing My MTA's Poor Reputation

I have a web site that needs to send email to customers to deliver files that they have purchased. Reliable email delivery is vital to this business. Unfortunately, most of the emails sent by my ...
17
votes
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 ...
16
votes
6answers
15k views

How to Setup Ubuntu Mail Server with Google Apps?

I have a domain, let's call it foobar.com. All of the MX records for foobar.com point to Google's mail servers because I am using Google Apps for your domain to manage it. It's great because everyone ...
15
votes
3answers
14k views

Automatically start SMTP server in IIS?

I'm running an IIS SMTP server in Windows 2008 R2 and it can be started manually. However, if I need to restart the system, I must manually start the SMTP server. Is there a way for it to start ...
15
votes
2answers
14k views

Correct use of SMTP “Sender” header?

Our web application sends email messages to people when someone posts new content. Both sender and recipient have opted into receiving email messages from our application. When preparing such a ...
15
votes
11answers
85k views

IIS/SMTP - emails are stuck in mailroot/Queue

I'm trying to send e-mails via SMTP within the IIS pickup directory. Unfortunately the e-mails are just going into the mailroot/queue folder and stay there. They never actually get sent. Does ...
14
votes
1answer
2k views

Security risk of POP before SMTP

I received an email from one of our servers this morning (CentOS, with WHM running LAMP) stating: The server has POP3 before SMTP enabled. For security reasons, cPanel highly recommends that ...
14
votes
5answers
12k views

What host name should the SSL certificate for an SMTP server contain?

I have a server foo.example.com at 192.0.2.1 It runs exim to receive e-mail for several of my domains. My domains each have an MX record pointing to mx.example.com, which resolves to 192.0.2.1 If I ...
14
votes
1answer
5k views

Postfix TLS over SMTP - RCPT TO prompts renegotiation then 554 5.5.1 Error: no valid recipients

I've setup ispconfig3 on my debian six server, and here is a little smtp over ssl: The server is postfix AUTH PLAIN (LOL!) 235 2.7.0 Authentication successful MAIL FROM: lol@lol.com 250 2.1.0 Ok ...
14
votes
3answers
3k views

Schedule/queue large e-mails in Exchange 2010, defer until latency drops

My challenge We have Exchange servers at various sites, but also aboard ships. The ships are connected to our network through satellite links when at sea, but switch to WiFi bridges when in port. ...
13
votes
2answers
1k views

Gratuitous CRLF in Subject: line - why is it there, and is it legal?

I'm running into a problem with a NAGIOS system sending emails to a popular email-to-SMS service. The email-to-SMS service takes emails with text in the Subject: line, and sends them on to the mobile ...
12
votes
8answers
43k views

Send an email with an attached file using telnet or netcat

I often use telnet or netcat to connect smtp servers to send an email as a test. Does anyone know how you would send an email using telnet or netcat but attach a file as well? There are probably ...
12
votes
4answers
22k views

What are SMTP relays and smarthosts?

What exactly is an SMTP relay, and what exactly is an SMTP smarthost? Can someone give me a brief description of each, including how they relate to one another?
12
votes
2answers
872 views

Is it still “wrong” to require STARTTLS on incoming SMTP messages

According to the STARTTLS Spec Section 5: A publicly-referenced SMTP server MUST NOT require use of the STARTTLS extension in order to deliver mail locally. This rule prevents the STARTTLS ...
11
votes
5answers
145k views

Reverse DNS - how to correctly configure for SMTP delivery

I started a new service and we need to send emails to our customers (new account confirms, etc). My server is known as prod01.bidrodeo.com and resolves to 97.107.134.38 . For reverse DNS, 97.107....
11
votes
4answers
13k views

Legitimate reasons SMTP “MAIL FROM:” will not match “From:” Header in DATA

Is there ever a legitimate reason for the SMTP “MAIL FROM:” field to not match the “From:” field in the DATA section of a message, besides mailing lists? From http://stackoverflow.com/questions/...
11
votes
4answers
2k views

Has anyone ever used SMTP site links?

A simple real-life question, inspired by a comment here: Active Directory has supported inter-site replication using SMTP instead of direct RPC since its first introduction in Windows 2000. But did ...
10
votes
7answers
2k views

Does SMTP greylisting a) stop much spam and b) stop much legitimate mail?

I've just set up an SMTP server on a relatively little used domain using Postfix and enabled greylisting with SQLGrey. So far it seems to be working OK, and while there's the slight irritation of ...
10
votes
2answers
2k views

SMTP allows for multiple FROM addresses in the RFC. Was this ever useful, why does this exist?

SMTP allows for multiple FROM addresses on the body (not the envelope) according to the RFCs. Has this feature ever been used for a legitimate purpose? Is it safe to discard messages that have ...
10
votes
3answers
286 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 ...
10
votes
4answers
17k views

When exim4 sends HELO/EHLO, how do I configure which host name it sends?

Mails from my system are being rejected when the receiving server does HELO checking. I believe my system is sending the wrong domain name. I'm running exim4. Googling for anything about exim4 and ...
10
votes
2answers
6k views

Are two periods allowed in the local-part of an email address?

A third-party email gateway relay is refusing to process a message for an email address we're sending to. The address is in the format of firstname..lastname@recipientdomain.com (note the two periods)...
10
votes
2answers
38k views

Postfix - Host or domain not found

I just installed Postfix on my ubuntu, on a local network. On this network, I have an Exchange Server (using domain mail.example.com). I had a problem sending an email to a local address : adress@...
10
votes
5answers
2k views

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 ...
10
votes
1answer
10k views

What is preferable, “no-reply@” or “noreply@”? [closed]

Having a service that sends out notifications to users, I'm currently thinking about changing the sender email address from "info@" to something more meaningful. Since a reply never makes sense, I'm ...
10
votes
1answer
162 views

What takes precedence: an SPF record with “-all” in the primary TXT record, or one in the “include” section?

Suppose I have a domain (company.com) with an SPF that looks like this: v=spf1 ip4:70.70.70.70 include:host.marketing.com -all and "host.marketing.com" looks like this v=spf1 ip4:8.8.8.8 ~all ...
10
votes
2answers
5k views

What is the best method for sending email on behalf of my clients' domains?

I wanted to know the best way to make my mailserver send emails on behalf of my clients' domains, without being greylisted and also avoiding bounce problems. I've been reading some other questions ...
9
votes
4answers
11k 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?
9
votes
2answers
20k views

How to fix “unable to qualify my own domain name (myhost) — using short name”? [closed]

and yes, I have 127.0.0.1 localhost myhost.mydomain.eu myhost.domain2.eu localhost.localdomain 127.0.1.1 myhost in hosts file. What is wrong? Sendmail started to put this error into log. ...
9
votes
1answer
6k views

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 ...
9
votes
3answers
62k views

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 ...
9
votes
3answers
191 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? ...
9
votes
2answers
163 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 ...
8
votes
5answers
2k views

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 ...
8
votes
5answers
7k views

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 ...
8
votes
8answers
33k views

How to configure php.ini with remote SMTP?

How do I configure PHP to send mail using mail() via a remote SMTP server? I've tried to do this using php.ini but it seems that you can only do that under Windows32 and I want to do this on my Unix ...
8
votes
2answers
9k views

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 (...
8
votes
4answers
14k views

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 ...
8
votes
1answer
592 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 ...
8
votes
2answers
12k views

Why is Postfix trying to connect to other machines SMTP port 25?

Jul 5 11:09:25 relay postfix/smtp[3084]: connect to ab.xyz.com[10.41.0.101]:25: Connection refused Jul 5 11:09:25 relay postfix/smtp[3087]: connect to ab.xyz.com[10.41.0.247]:25: Connection ...
8
votes
4answers
614 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 ...
8
votes
1answer
8k views

NOQUEUE: reject: RCPT from on freebsd and postfix

I am building a server using this config -> http://www.purplehat.org/?page_id=4 and when trying to test basic email capabilities I get -> NOQUEUE: reject: RCPT from when try to send a test email. ...
8
votes
2answers
405 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 ...