Solved

SMTP: RCPT TO: always empty, instead DATA TO: ?

Posted on 2004-09-06
6
1,827 Views
Last Modified: 2008-02-26
Hey guys,

While programming an application using SMTP, I found this very confusing thing.

Every article, manual, document, you name it, covering SMTP tells me that recipients are added using the RCPT TO: <address@domain.tld> command. However, when I manually send an email using telnet, when I look in my mail root directory (eg. inetpub/mailroot/queue), the email I just sent always lists the 'To:' field as empty, for example when I load the email in Outlook.

After much messing around with it and asking a friend of mine, it seems that the only way to get the 'To:' field to contain addresses, is by setting it in the DATA field. For example:

EHLO
MAIL FROM: me@mydomain.net
RCPT TO: you@yourdomain.net
DATA
Test email
.

If I load this email in Outlook (or edit in a texteditor) it clearly shows that the mail is from me@mydomain.net, with no subject, body 'Test email', but no recipient! However if I do this:

EHLO
MAIL FROM: me@mydomain.net
RCPT TO: you@yourdomain.net
DATA
TO: you@yourotherdomain.net
Test email 2
.

it will show the email to come from me@mydomain.net, no subject, body 'Test email 2' but with recipient you@yourotherdomain.net?!

This confuses me, especially since I can't seem to find an article covering this. Also, what is the point of the RCPT TO: field when somehow it won't accept this for me? Oh and I tried this on 2 different SMTP servers, using remote connections or local connections, so I don't think there can be the problem.

I hope someone can explain this to me! Thanks!

Razzie
0
Comment
Question by:Razzie_
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
6 Comments
 
LVL 34

Accepted Solution

by:
PsiCop earned 100 total points
ID: 11992856
Simply put:

TO: != RCPT TO:

This took me awhile to figger out to.

RCPT TO: is an SMTP command that tells the MTA (Message Transfer Agent) to whom the E-Mail is destined. This is so it can perform lookups, determine if it accepts mail for this Domain and/or user, determine proper routing, etc. etc.

The TO: line in an E-Mail derives from the headers transmitted with the E-Mail itself. That is, your program must *explicitly* transmit a TO: header, during the DATA step, if you want the resultant E-Mail to have a TO: header. RCPT TO: is strictly for the MTA.

This is how things like BCC: are done. The recipients are listed in the RCPT TO: commands during the initial communication with the MTA, but the TO: header is omitted. TO: is mainly for us humans, (and any programs, like ProcMail, that may handle the E-Mail after the MTA has accepted it for delivery).
0
 
LVL 34

Expert Comment

by:PsiCop
ID: 11992908
Whoops. That was my site.Config.m4 I gave you a link to above. Here is my annotated sendmail.mc

http://www.experts-exchange.com/Networking/Email_Groupware/Sendmail/Q_21116293.html
0
 
LVL 34

Expert Comment

by:PsiCop
ID: 11992939
Fudge. Wrong Question. Ignore my last Comment.
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 
LVL 8

Author Comment

by:Razzie_
ID: 11994610
Ok thanks PsiCop!
0
 
LVL 8

Author Comment

by:Razzie_
ID: 11994613
Btw, it's strange that all articles I read about SMTP do not cover this, I wonder why....
0
 
LVL 34

Expert Comment

by:PsiCop
ID: 11996905
I dunno. I'll Ask Mr. Protocol if he can look into it.
0

Featured Post

Veeam gives away 10 full conference passes

Veeam is a VMworld 2017 US & Europe Platinum Sponsor. Enter the raffle to get the full conference pass. Pass includes the admission to all general and breakout sessions, VMware Hands-On Labs, Solutions Exchange, exclusive giveaways and the great VMworld Customer Appreciation Part

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

The biggest nightmare for any Exchange Server Administrator is to keep the server running without any issue. But the problems often come and they need to be resolved efficiently and timely. Here are important troubleshooting points: Define the Pr…
I tend toward trying the newest hardware and software.  Thiss sometimes works out to my benefit, and sometimes not.  Because I downloaded and installed Android 5.x (http://www.experts-exchange.com/articles/18084/Upgrading-to-Android-5-0-Lollipop.htm…
The purpose of this video is to demonstrate how to set up a Mailchimp Template which will let the user create a uniform look for all of their campaigns. This will be demonstrated using a Windows 8 PC. Mailchimp will be used. Log into your Mail…
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …

623 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question