|
|
Sponsored Content
Top Forums
UNIX for Dummies Questions & Answers
Unix mail command internals
Post 302555741 by Corona688 on Thursday 15th of September 2011 12:39:58 PM
09-15-2011
How email's mostly used now is way different from how it originally worked. SMTP used to be something email servers used to push email to other email servers, not something clients used.
Client A would dial directly into a shell on server B, and send a message, ultimately, through sendmail, which talks directly to the server's own mail-transport agent(MTA). If the destination was on the same server, the email would be directly transferred to the recipient's maildir folder without any networking required at all. If the destination was on server C, the MTA would eventually need to open an SMTP connection elsewhere to transfer it. (It needn't do so instantly. It needn't do so directly, either. It might send to server E, which would forward to server C, etc.) Client D would dial into server C and check their local maildir folder for files to see if any mail had arrived.
In short, commandline mail didn't use an SMTP server -- commandline mail was an SMTP server. That's mostly how it remains.
Once home computers started getting network access, users were able to access POP and SMTP and IMAP to get mail remotely instead of directly shelling into your mail server, but the design of UNIX MTA's still reflects having local mail for local users.
There's lots and lots of different MTAs now. With few exceptions, they all look the same on the surface -- they all give you a commandline sendmail program to send mail with, etc. Many of them still even use configuration files based on ones the venerable sendmail server used -- even though their capabilities can be radically different. I suspect that's why trying to configure an MTA has involved so much brain damage for me. Others have suggested that the damage was there already
If all you want to do is have sendmail forward to existing email addresses somewhere else, I wouldn't bother setting up a full-fledged MTA. ssmtp is a tiny sendmail replacement which doesn't do any MTA duties at all, its sendmail command directly connects to remote SMTP servers of your choosing, like an ordinary email client would.
Client A would dial directly into a shell on server B, and send a message, ultimately, through sendmail, which talks directly to the server's own mail-transport agent(MTA). If the destination was on the same server, the email would be directly transferred to the recipient's maildir folder without any networking required at all. If the destination was on server C, the MTA would eventually need to open an SMTP connection elsewhere to transfer it. (It needn't do so instantly. It needn't do so directly, either. It might send to server E, which would forward to server C, etc.) Client D would dial into server C and check their local maildir folder for files to see if any mail had arrived.
In short, commandline mail didn't use an SMTP server -- commandline mail was an SMTP server. That's mostly how it remains.
Once home computers started getting network access, users were able to access POP and SMTP and IMAP to get mail remotely instead of directly shelling into your mail server, but the design of UNIX MTA's still reflects having local mail for local users.
There's lots and lots of different MTAs now. With few exceptions, they all look the same on the surface -- they all give you a commandline sendmail program to send mail with, etc. Many of them still even use configuration files based on ones the venerable sendmail server used -- even though their capabilities can be radically different. I suspect that's why trying to configure an MTA has involved so much brain damage for me. Others have suggested that the damage was there already
If all you want to do is have sendmail forward to existing email addresses somewhere else, I wouldn't bother setting up a full-fledged MTA. ssmtp is a tiny sendmail replacement which doesn't do any MTA duties at all, its sendmail command directly connects to remote SMTP servers of your choosing, like an ordinary email client would.
Last edited by Corona688; 09-15-2011 at 01:55 PM..
This User Gave Thanks to Corona688 For This Post:
|
|
10 More Discussions You Might Find Interesting
1. New to Unix. Which books should I read?
Hi!
I have 1.5 years experience in unix environment and shell scripting. Now, I started learning UNIX internals and network programming. Can you please help in finding the same material on the net
Thanks
Srinivas. (7 Replies)
Discussion started by: srinivaskathika
7 Replies
2. Filesystems, Disks and Memory
will anybody tell me how can i access all the fields of process table .if there is any structure and a system call please specify . (1 Reply)
Discussion started by: vish_shan
1 Replies
3. UNIX for Dummies Questions & Answers
hi,
Im trying to send a e-mail to two people e.g X & Y . I run a shell script that uses the mail command to send an email to both these people . The email that i am sending contains two attatchments that i 'add' to a .mail file.
mail <recipients> < filename.mail
The problem that im... (1 Reply)
Discussion started by: nbvcxzdz
1 Replies
4. Programming
I know UNIX user level commands, shell scripts. But i have no idea about kernel level programming and networking. I know the terms semaphore,IPC,socket programming. But i don't know in details what are these. I need to know the following.
1. Unix kernel level programming.
2. Unix Internals.
3.... (4 Replies)
Discussion started by: digdarshan
4 Replies
5. UNIX for Dummies Questions & Answers
1)My main script Calls a function IsDomain to check whether the domain is valid or not
PROD>/appl/retek/mpscripts/cat mg3TRn01
#!/bin/ksh
#
# Standard Header Files
#
#
. ${0%${0##*/}}UKMPFunctionLibrary.test
#
# START
#
ScriptStart
#
# Check that domain exists.Print &... (0 Replies)
Discussion started by: Shilpi
0 Replies
6. UNIX for Dummies Questions & Answers
Hello,
When i am using mail command like this:
mail -r prashant.aggarwal@xx.com -s "hiiii" prashant.aggarwal@xx.com < Content.txt i am abl eto dend a mail. Content.txt is a file from which contents are being reda
But when i am trying to execute it thru a shell scipt like this it's giving ... (3 Replies)
Discussion started by: cprash.aggarwal
3 Replies
7. UNIX for Dummies Questions & Answers
I recently generated myself the following error when attempting to use the Unix mail command:
The flags you gave make no sense since you're not sending mail.
There is a recent thread about this issue here in unix.com (with a title very much like this thread's title), but it was closed... (2 Replies)
Discussion started by: Clovis_Sangrail
2 Replies
8. Shell Programming and Scripting
Hi All,
Is it possible to email a file from another directory in Unix shell prompt? In other words, do we have to be in the directory where the file is located to mail the file?
I was in the Mail directory and my file (filename) is in the Practice directory. I tried this and it didn't work:... (7 Replies)
Discussion started by: onlinelearner02
7 Replies
9. What is on Your Mind?
Hello,
Long-time Unix hacker here - I've worked on four variants of the kernel prior to the introduction of Linux. In my spare time, I've written Linux (Ubuntu) device drivers, kernel modules, cross-compiled, and built the kernel.
I'd like to do Linux internals/device drivers as a day job,... (1 Reply)
Discussion started by: OriginalVersion
1 Replies
10. Shell Programming and Scripting
I am using HP-UX server. I tried to send the email with attachment, I used the below unix command to send with attachment but it doent work.
uuencode pepsitoday.csv | mailx -s "csv file" ramkumar15@pepsi.com
---------- Post updated at 02:10 AM ---------- Previous update was at... (2 Replies)
Discussion started by: ramkumar15
2 Replies
LEARN ABOUT SUSE
calibre-smtp
CALIBRE-SMTP(1) calibre CALIBRE-SMTP(1) NAME
calibre-smtp - part of calibre SYNOPSIS
calibre-smtp [options] [from to text] DESCRIPTION
Send mail using the SMTP protocol. calibre-smtp has two modes of operation. In the compose mode you specify from to and text and these are used to build and send an email message. In the filter mode, calibre-smtp reads a complete email message from STDIN and sends it. text is the body of the email message. If text is not specified, a complete email message is read from STDIN. from is the email address of the sender and to is the email address of the recipient. When a complete email is read from STDIN, from and to are only used in the SMTP negotiation, the message headers are not modified. Whenever you pass arguments to calibre-smtp that have spaces in them, enclose the arguments in quotation marks. OPTIONS
--version show program's version number and exit -h, --help show this help message and exit -l, --localhost Host name of localhost. Used when connecting to SMTP server. -o, --outbox Path to maildir folder to store failed email messages in. -f, --fork Fork and deliver message in background. If you use this option, you should also use --outbox to handle delivery failures. -t, --timeout Timeout for connection -v, --verbose Be more verbose COMPOSE MAIL Options to compose an email. Ignored if text is not specified -a, --attachment File to attach to the email -s, --subject Subject of the email SMTP RELAY Options to use an SMTP relay server to send mail. calibre will try to send the email directly unless --relay is specified. -r, --relay An SMTP relay server to use to send mail. --port Port to connect to on relay server. Default is to use 465 if encryption method is SSL and 25 otherwise. -u, --username Username for relay -p, --password Password for relay -e, --encryption-method Encryption method to use when connecting to relay. Choices are TLS and SSL. Default is TLS. SEE ALSO
The User Manual is available at http://calibre-ebook.com/user_manual Created by Kovid Goyal <kovid@kovidgoyal.net> calibre-smtp (calibre 0.6.53) July 2010 CALIBRE-SMTP(1)