programmatically sending out emails from a linux server - email

I want to send out one off emails from a linux server. The server does not need to receive emails back.
Is there a simpler solution than sendmail for sending outgoing emails only?
I would prefer to use Perl to send the email.


Calling out to /usr/lib/sendmail is usually the preferred method because it handles delivery problems correctly. This does not mean using sendmail. Most (all?) mail transport system provide a command that's just named sendmail and provides an interface compatible to the original.
Alternatively you can send directly through a SMTP relay using a package like Net::SMTP but be extra sure to correctly cater for delivery problems.


Sendmail is not the only choice. you can use Postfix, Qmail, and many others
my Perl scripts call the mailx command. to know how to use it, type 'man mailx'
However this require to have a MTA correclty configured.
Or you can just use the Net::SMTP perl library and use your smtp server of choice


I have used msmtp successfully, ie it supports great authentication
TJ Luoma did a nice writeup of it on TUAW


I find nullmailer a very useful solution for the described scenario. Nullmailer is a sendmail/qmail/etc replacement MTA which relays to a fixed set of mail servers. It is very simple to configure and consumes little resources.
One important advantage of nullmailer over other mentioned solutions like mstmp and ssmtp is that it maintains a queue of emails to be sent. The application sending the mail is blocked only a very short time while the mail is queued (milliseconds). The sending of the mail happens in the context of a another process.
Solutions like mstmp and ssmtp don't maintain a queue of email. The sending happens in the context of the application, thereby blocking the application. Sending an email this way can easily take 1 to 2 seconds or longer. This may not be a problem in many cases but can become a problem if the email is sent by a web application.
http://untroubled.org/nullmailer/


You do not need a mail transport agent (MTA) instance on the machine doing the sending if you have another mailserver already running in your organization: you can make Perl deliver the email through SMTP to that server, so there's no need for having (another) MTA like sendmail on "your" machine.


I'm fond of creating a gmail or other free account and then using the java mail api in J2EE to send messages (from your new gmail account) to whoever... Typically i'll create a Mailer class which can be constructed with a default constructor and then give it a send(String dest, String subj, String body[, Obj attach...if you want]) and then in your case you might wrap the thing in a main method so that you can call it from else with some command line args, or call from within some java program. If you interested i'll shoot you the code.


I know you said perl, but the simplest cross-platform email sending library I have used is python's smtplib. Certainly worth a look.

Related

Extendable or programmable mail server

Is there any extendable mail server that can implement a service like a chat robot?
I think what I am looking for is a middleware based on SMTP.

Most unix MTAs can do that. One way is to make a login called foo so that you have an email address foo#example.org. Then you put |/home/foo/program into /home/foo/.forward. Now /home/foo/program will be invoked on each incoming mail, receiving the message content as input.
There's a program called formail which may be quite handy (if you write in sh).

I found this library and it provides exactly what I need.
https://code.google.com/p/subethasmtp/

procmail and delivering to an IMAP server?

I run my own mail server. It uses procmail to filter incoming mail, which is then stored in maildirs and gets served out my MUA using IMAP. I've got about 1.5GB of email is 135000 inodes.
This all works very nicely. However, I'd rather like to stop using maildir and switch to something more efficient --- maildb, or Dovecot's dbox, for example. Unfortunately, procmail can only deliver to a very limited set of backing store formats (Maildir, MH and mbox, AFAICT).
What I'd really like to do is to persuade procmail to deliver email via IMAP, rather than writing it directly to the backing store; this means that I can change the backing store format whenever I like without needing to reconfigure procmail. But I can't find any way of doing this. Any ideas?
(I'm also interested in any other mail filter tools that work like procmail but support IMAP. The only other filter tool I know is maildrop --- but that has similar restrictions to procmail.)

Okay, here's a proper solution.
The cone project (http://www.courier-mta.org/cone/cone00index.html, Debian project: cone) has a very handy tool called mailtool which will copy files between mailbox types, including remote IMAP servers.
So, to deliver a message to a remote mailbox, you need a script which:
writes out the incoming message to a file (which becomes a one-message mbox folder)
does mailtool -tofolder destinationfolder -copyto imaps://username:password#server.com mbox:/full/path/to/message.mbox
That will then upload the message.
I don't actually need to do this any more so don't have a prepared script to post, but of the eight or nine different IMAP tools available, this was the only one that would actually do this, so it's worth documenting as such.

As a partial answer to my own question, it seems that Dovecot does come with a deliver tool specifically designed for this kind of thing; it works from procmail with a line like:
| /usr/lib/dovecot/deliver -m "Folder.Name"
...and it figures out all the rest of the settings automatically.
So now I can change the Dovecot mail storage format and everything will still work; but I'd still like an approach that actually uses IMAP to deliver the messages, so that I can try IMAP servers other than Dovecot's.

What's the easiest way to process incoming email and add it to a queue on a Linux server?

What's the easiest way to process incoming email? Our objective is to get email into a Resque queue. We've explored and integrated a lot of options, like piping email through Postfix into Ruby (which turned out to be unreliable), piping email through Google App Engine back to our server (which turned out to be shaky), and using Sendgrid (which is expensive.)
I'm trying to explore other ways to get email processed. Any ideas?

If the email is received and hosted by an IMAP-capable server (Gmail is good enough), then the messages can be retrieved and processed once and again from almost any programming language using standard libraries.

Sendmail runs a smtp server(daemon) in the background?

I am relatively new to arena of emails. Just drilling out tutorial by tutorial about email internals. My requirement is I need to send emails and receive emails from my webhost. For this to happen, I need an smtp server(daemon) running right? I recently studied about MTAs, which are responsible for transferring emails from one host to the other. So this smtp server(daemon) acts as an MTA. And I also studied sendmail is an MTA, which boils down to sendmail runs a smtp daemon in the background. Right?

It's probably fairer to say that sendmail is an SMTP daemon than to say it runs one, since sendmail is pretty monolithic. But basically you have it right - in order to receive email, you need an MTA listening on port 25 when an incoming connection comes. There are many choices for an MTA. I prefer postfix because it's not monolithic, it has a very easy to read config file, and it has a good security model. Other good choices are exim and qmail.
For outgoing mail, you need a program that can figure out where the mail is supposed to go, and make a connection to that receiver's port 25. Once again, just about any MTA will do that for you, but some programs that want to send mail will attempt to do it directly instead of invoking the local MTA. The problem with that is that they then have to duplicate all the things MTAs give you, such as knowing how to fall back and retry when the mail receiver can't be reached.

You need to run daemon to receive emails and to resend emails if they failed to be sent for some reason.
To send them, you just invoke sendmail which will connect to the destination's sendmail (which, of course, runs as a daemon), send you mail and exit.
If you sending this from a website, you may use mail functions of your scripting language, because spawning a process is quite costly thing under a heavy load.

Method for email testing

I am writing a program that will be emailing reports out many (~100) clients which I want to test before I spam everyone.
I want to do a test run against my production data and actually send the messages to a SMTP server, but I don't want the SMTP server to actually deliver the messages. I want the server to act like a real SMTP server from the perspective of my application, but instead of delivering messages, I just want it to store the messages, and log what happened.
Is there a SMTP server specifically designed for testing purposes?
Does anyone know of a way to configure exim or postfix to behave like I have described above
What do you use to test a mass-email delivery?

In java you can use dumbster
Its easy to use and you can validate every aspect of the email you are intercepting.
It's a Java SMTP server implementation meant for unit testing. (Just make sure you redirect your email to the machine running dumbster...)
I just found another alternative that do almost the same: Greenmail
Greenmail also support POP3, IMAP with SSL so you can test your client against it.

For .NET I set the config file to deliver mail to a folder, then you can have the automated test inspect the directory and files.
<system.net>
<mailSettings>
<smtp deliveryMethod="SpecifiedPickupDirectory">
<specifiedPickupDirectory pickupDirectoryLocation="c:\pickupDirectory"/>
</smtp>
</mailSettings>
</system.net>

While searching for options I found the following that may be useful.
DevNullSmtp
Use a null SMTP server for testing
Fake SMTP Service
twisted examples/emailserver.tac

"The Wiser framework for unit testing mail"
I've heard of a few other developers moving from Dumbster to Wiser and have migrated my testing code as well. One of the Java components that I've worked on sends thousands of emails a day and I've written unit tests for the different email templates and scenarios using Dumbster and Wiser. I prefer Wiser.
Snips from the Wiser website (http://code.google.com/p/subethasmtp/wiki/Wiser):
Wiser is a smart replacement for Dumbster and is built on top of the SubEtha SMTP Java library which allows your Java application to receive SMTP mail with a simple, easy-to-understand API.

A good program for email testing is smtp4dev (Windows only).
It's a dummy SMTP server. Sits in the system tray and does not deliver the received messages. The received messages can be quickly viewed, saved and the source/structure inspected.
http://smtp4dev.codeplex.com/

http://skaraarslan.blogspot.com/2008/02/how-to-check-email-works-without-using.html
(this presumes you are using .net to send emails)

Given that you mention exim and postfix (which I'm taking to be some kind of unix stuff), this answer might not be as useful as it could be, but check out Neptune. It's a fake SMTP server designed for automated testing. If you've got a spare windows box floating around, you could put Neptune on that then configure your app to send "through" the Neptune server.

Exim can be configured to accept incoming mails but not deliver them. Look for the keywords queue_only and queue_only_file in the documentation.

I personally modify the e-mail addresses to test, I send them to a dummy account of mine, that way I can validate not only that they sent, but that they appear in the proper format.

At my office, we have a server that is set up to always send all incoming mail to one address, regardless of who it's actually addressed to. We just point all our testing environments at that server and watch the QA mailbox fill up. I don't know what server it is, but it's probably some open source thing someone found.

Sendmail has a Test Mode.
You just invoke sendmail with the -bt parameter. As an example:
/usr/lib/sendmail -bt -Ciu-testconfiguration.cf
Please be aware that in this method, Sendmail requires an special configuration on rewrite rules. You need to understand how Sendmail rewrites addresses in order to properly create a .cf file for Test Mode.
Edit: See this article: http://ussg.iu.edu/usail/mail/debugging/

After not beeing happy with the solutions I found, I ended up writing developmentSMTP, easy to use, 100% Java --> cross platform.
Supports writing emails to file, forwarding emails or simply printing them on stdout.

Post Hoc is a pure Java application that looks exactly like an SMTP server to the application you are testing, but it simply collects all the email messages and allows you to inspect them using a web interface.
Freely available at: Post Hoc GitHub Site
For more information: PostHoc: Testing Apps that Send Email

If you're looking to manually test that the email sends and that the email template has the right kind of html and css that you're expecting, then I would recommend maildev https://www.npmjs.com/package/maildev. You can install and run it as a node module and also as a docker container! I've found it extremely handy for basic sanity testing of emails.