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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Mail relays or SMTP services for use in code

I'm looking to start using an SMTP or mail relay service. I've found quite a few out there, but I'm not sure if there are advantages to one vs another. The only requirements I have are: can send ...
3
votes
1answer
170 views

Is Sender Policy Framework (SPF) effective in preventing Phishing emails?

As defined in RFC4408, Sender Policy Framework only checks the envelope sender (aka MAIL FROM). The From: header is not being tested. As it is the value of the From: header which is usually displayed ...
2
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6answers
372 views

How to centralize my mail?

I get a bunch of mail on about 20 different servers that I'd like to get to one. The boxes are running Linux and right now my solution is to create a TCP relay. I want anytime traffic coming in on ...
2
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3answers
868 views

SMTP session between 2 mail servers on the internet: Without authentication?

I have some basic question about SMTP (try not to laugh too much). When i try to use SMTP via telnet to send email on google it requires authentication. Mail servers use SMTP to relay messages ...
2
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2answers
343 views

How do I log tls-encrypted smtp traffic?

I'd like to know what my local postfix says to the Amazon SES smtpd after the STARTTLS. In plain text, so I can understand it. Amazon SES requires TLS, so I can't temporarily turn it off. I currently ...
2
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4answers
642 views

A flexible SMTP server that's open source or free [closed]

We currently have our own in-house email marketing software for our newsletters, and were using SQL server's SMTP agent to send emails through our local SMTP server (IIS) and then onto our ISP's SMTP ...
2
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3answers
1k views

Postfix or exim: Automated/Programmatic and forwarded email setup

I'm looking to replace our current use of an external smtp provider with an in-house installation. It should handle the following situations: Certain addresses should be forwarded to gmail ...
2
votes
3answers
89 views

In a linux-based email server, how can one prohibit SMTP/IMAP/POP connections from clients while still using Webmail (Roundcube)?

With a fully functioning linux-based email server (running postfix/Dovecot) how can one disable the ability to connect to SMTP/POP3/IMAP with external mail clients (or telnet, etc) while still (and ...
2
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6answers
185 views

Does disallowing sending emails via a SMTP server that doesn´t have the same address help preventing spam or is it dangerous?

I am working in a small programming company and administrated the mail-servers for quite a while. Now we moved our web site and the MTA to a company that we considered to be more professional. But I ...
2
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3answers
277 views

Postfix + Php Mail() VS Postfix + SMTP

Most CMS (Joomla for example) comes with php mail() as default and has the option of changing it to SMTP if we want. I will be setting up both the webserver and mail server (Postfix) in the same VPS ...
2
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1answer
2k views

ERROR: Message not sent. Server replied: 354

On webmail every user gets error "ERROR: Message not sent. Server replied: 354" while sending mails. But mails are sent properly and reaches properly. Can you tell me where is problem, and why it ...
2
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2answers
6k views

What might cause a user to receive duplicate emails?

One of our customers is receiving duplicate emails from our application, even though as far as I can tell from the application and SMTP logs, we're only sending it out once. What are some of the ways ...
2
votes
1answer
199 views

What domain should I use for reverse DNS PTR record?

If setting up a mail server. What is the best domain to use for the IP's PTR record? Is it usually better to use "mail.domain.com" or just "domain.com" ? I understand that If the PTR record is set, ...
2
votes
1answer
185 views

Issue of tracking an email that was “lost in cyberspace”

The issue here is one of an email that has been "lost in cyberspace." The receiver is claiming never to have received it. However, I recieved an automated out-of-office reply as a response to my ...
2
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6answers
363 views

I'm hosting reseller and I got spam problems. Please help to solve

Our provider suspended our account with 5000+ clients and their sites. The reason was that the whole IP range was blacklisted by SpamHouse, but our provider did not explain what emails, form what IP ...
2
votes
3answers
4k views

UNIX: Send Mail using SMTP Server

I would like to send an email through a remote SMTP server. How can this be done? I will be sending the email from a bash shell script. I'm using a unix machine. uname -a returns: Linux linux 2.4.21 ...
2
votes
2answers
3k views

Problems opening port 465 for smtp on centos

I'm using phpMailer to send off purchase confirmations using a google apps address/smtp. The whole thing was working great on the development box, but now that it's live, it seems that the port I'm ...
2
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2answers
713 views

Is there a way to completely disable outbound opportunistic TLS support in SendMail?

CentOS 5.x SendMail 8.14.4 An overzealous network security feature is causing TLS negotiations to fail when my Sendmail server tries to talk to external hosts. This is causing sendmail to constantly ...
2
votes
3answers
2k views

SMTP stress test

does anyone knows of any good software for Mac OS X or at least for RHEL/CENTOS Linux that I can run against my SMTP Server?
2
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3answers
144 views

How to isolate Google Gmail SMTP server IPs directly?

I am performing some custom routing with a VPN in the mix that is requiring me to add each Google Gmail SMTP server IP to the routing table so that they pass over another gateway than the VPN's ...
2
votes
1answer
227 views

Maximum length of MAIL FROM address

When sending out emails with a MAIL FROM address > 81 characters I receive bounce messages from some MTAs: 501 Syntax error - Badly formatted address. (in reply to MAIL FROM command) As soon as ...
2
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2answers
1k views

Postfix - accept all email to any user at any domain

I need to configure an SMTP server to accept any email to any address that might happen to reach it on port 25 and deliver it to a local mailbox (i.e. a spam sinkhole) The default supported MTA on my ...
2
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3answers
289 views

small rootless SMTP server for linux?

Is there a SMTP server that can start on localhost without root privileges? Postfix and sendmail both require root to start. Update: To clarify both Postfix and sendmail require root to start even if ...
2
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2answers
516 views

Postfix with Dovecot configured and send emails with no errors. When sending from a remote client message-id is empty, and emails go to spam.

I have Postfix and Dovecot installed and running on the VPS. Using telnet once from VPS, and once from a client machine, I'm composing exactly the same messages. Everything is working but when sending ...
2
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2answers
115 views

Does a receiving mail server (the ultimate destination) see emails delivered directly to it vs. to an external relay which then forwards them to it?

Let's say my users have accounts on some mail server mail.example.com. I currently have my mx record set to mail.example.com and all is good. Now let's say I want to have mails initially delivered ...
2
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3answers
103 views

Is it possible to cause email to my domain to be handled by gmail?

[This is a very narrow question, and I don't think it is covered in similar sounding questions] I want to configure my server's DNS so that when someone sends email to me@myserver.com it is actually ...
2
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1answer
6k views

Postfix + SASL = “Relay Access Denied” when sending from outside the network

I have in /etc/postfix/main.cf: smtpd_sasl_auth_enable = yes smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination and SASL seems to be working: $ ...
2
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2answers
193 views

Multi-site email relay based on email address (in AD?)

We have a multi site setup currently based around Exchange 2003, but we are getting a lot of traffic over the vpn as only one server has an internet facing IP. Is there such a product that could sit ...
2
votes
1answer
7k views

Question on SendMail daemon actions when load average is too high

My sendmail server started rejecting connections because load average was too high (due to a spam issue that has since been resolved). Error was: sendmail[13400]: rejecting connections on daemon ...
2
votes
2answers
5k views

Cisco ASA rewritting SMTP traffic to prevent mail sending

We have a Cisco ASA 5505 (version 8.0(4)) that is preventing outbound SMTP traffic; testing with telnet shows connections on port 25 are having everything converted to *s while the same does not ...
2
votes
1answer
3k views

sendmail vs smtp server

I currently don't have a SMTP server setup. However, in my PHP code, I send all my SMTP request to sendmail. Are there any down fall to using this procedure? If yes, what are the advantages of ...
2
votes
1answer
894 views

Obtaining scans from HP LaserJet CM2320mf via email

I am trying, since I purchased the laser printer, to use the scan to email functionality, so far to no success and no lack of trying. The printer does not support sending emails via authentication. ...
2
votes
2answers
3k 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: 1. Deny relaying ...
2
votes
1answer
131 views

Postfix rejects SASL auth when dovecot is down

We're using Postfix with Dovecot and SASL Auth via Dovecot (based on this tutorial). All works like expected. But when Dovecot is down (i.e. for maintenance or other reasons) then clients could not ...
2
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1answer
532 views

Nginx Ubuntu Postfix Config - Can't connect to incoming IMAP server 'server not responding' but can send mail via outgoing using same details?

I'm pretty to new server admin and especially nginx but seem to be getting ok fine apart from accessing my mail via my iPhone? I've changed my domain to 'domain.com' The thing is I can send mail ...
2
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2answers
1k views

Some senders from external domains receiving “User Unknown” Errors

As far as I can tell, this question doesn't already exist here but if it does then I apologize. As of January 1st our company name has changed and, as such, our e-mail addresses have changed. The ...
2
votes
3answers
3k views

How to get Postfix to send/forward/relay to a sub-domain located on another server?

I have a quick question. How do I setup postfix to send an email to another server (Exchange Server) when sending to an email address that has a sub-domain of our main server. For example, say our ...
2
votes
1answer
2k views

Test SMTP security with OpenSSL?

I'm getting ready to deploy a new SMTP server, and I'm not sure how to ensure that it is using strong encryption. The server software is Postfix running only SMTP. I've added the following to the ...
2
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2answers
128 views

Connecting to Postfix via TLS

First off, I'm a programmer without much experience in programming with network protocols. That being said, I'm attempting to connect to a Postfix SMTP server using a secure connection. The ...
2
votes
2answers
668 views

Has this server been compromised?

A friend is running a VPS (CentOS) His business partner was the sysadmin but has left him high and dry to look after the system. So, I've been asked to help out in fixing an apparent spam problem. ...
2
votes
2answers
123 views

Postfix rejects mails if policyd is not reachable

I got a postfwd daemon running and it does a great job. smtpd_recipient_restrictions = [...] check_policy_service inet:192.168.10.7:10040 But if this server (192.168.10.7) isn't ...
2
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1answer
1k views

WSUS Email notification

Can i use gmail as SMTP server for wsus ?
2
votes
2answers
4k views

SMTP 552 4.3.1 Session size exceeds fixed maximum session size

I'm having a frustrating problem with one of our clients who is running an exchange SMTP server. I have an emailing component that is written in .net and I've specifically used Mono DLL's to ensure ...
2
votes
2answers
2k views

Postfix dynamic smtp_helo_name

I have a mail server that relays e-mails for two different domains. I want the smtp_helo_name to be different based on the domain. I'm assuming there is no way to do this via checking the mail ...
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2answers
2k views

Postfix relay with Exchange Server

Is it possible (or even logical) to use Postfix as relay MTA with Microsoft Exchange Server 2007, and if so how?
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2answers
2k views

IIS SMTP Service Routing Outbound Mail

Regarding the SMTP service that is including in Microsoft's Internet Information Services (IIS) 6.0. I have it in my mind that the built-in SMTP service is not capable of routing outbound messages, ...
2
votes
1answer
3k views

Mail domain authentication problems (error '553 sorry, that domain…')

What are the main causes of the following error and what sort of things would typically be checked to resolve it? 553 sorry, that domain isn't allowed to be relayed thru this MTA (#5.7.1) In this ...
2
votes
3answers
845 views

How do you configure sendmail to reject Email with a Date header too far from real time?

A friend of mine using (I believe) qmail has it configured to reject, as SPAM, any incoming Email with a Date: header that is too far from real time. I can't figure out how to do this with sendmail. ...
2
votes
1answer
176 views

cannot find postfix/mailx email in maildir, why not?

In a CentOS 7 development machine, I have configured postfix to allow emails to be traded between localhost addresses. Mailx is also installed. I am able to send email, and the log files indicate ...
2
votes
1answer
140 views

Centos SMTP error command not implemented

I have a vps with Centos 6.5 and postfix installed. When I want to connect to a smtp server like google or mail gun, I get the error 502 command not implemented. Can anybody help me please? This is ...