Sven Guckes ©1995-2003

Latest change: Thu Dec 11 06:00:00 CET 2003

HowTo Use the Reply-To Header Line

learn.to/use-reply-to

Situation: You send an email from address A to someone [S], but you want S to send his reply to your other address B.

        [You]  A --->  S  [Someone] --->  B [You]

The most natural way to do this is to tell the recipient to send his reply to that other address B. This is fine if you do it *once*, however, if you have to do it *every* time then this calls for an easier solution.

And there are several reasons why this can fail:

In all these cases there is a simple solution:

Make use of the Reply-To header line!

Put the other address B into the mail header within a "Reply-To" line - like this:

        Reply-To: Sven Guckes <reply-to-example@guckes.net>

Now the recipient's mailer will pick up that address automatically:

        To: Sven Guckes <reply-to-example@guckes.net>

All the recipient has to do for this to happen is to hit the usual key for "reply". No extra keys to type, no typos possible, no extra notes to send in the message. Simple! :-)

CAUTION: Some mail program do not seem to pick up the reply-to address. These programs are definitely *broken*, so it will not work with them. All mail programs however are required to follow a standard, and this standard specifies the Reply-To line and how it works. Every mailer has to comply to these standards. A mail program that does not follow this standard is broken! Please do not use broken mailers!


Other Situations

Using someone else's mailer. Sometimes you might find yourself in an enviroment where you just want to send an email using someone else's mailer. of course you do not want to change his setup - but you want the answer at your own address. in this case you would use the Reply-To: line to redirect the reply.

Special address. You might be using an address for sending mails out *only*, for example for a newsletter. Replies are more easily detected when sent to a special address. So set that special address into the Reply-To: line!

        From:      The Newsletter Guy <newsguy@company.com>
        To:        Company Newsletter <newsletter@company.com>
        Reply-To:  Newsletter Editor  <newseditor@company.com>


A typical change-of-address email

A Reply-To: line is often useful when you move from one address to another. Here is an example of such an email which makes use of the Reply-To: header:

   From:     me <current-address>
   To:       someone <elsewhere>
   Reply-To: me <new-address>

   Hi!  I have a new email address!  It is "<new-address>" starting next
   month.  So please update the mail alias that you may have for me from
   address <current-address> to my new address <new-address>.

   By the way, this mail has an additional header line ("Reply-To:")
   so that a reply to this mail should be addressed to my new account.

   greetings
   from
   me

Notes

There are some subtle things to look out for:

Reply-To:
The header name is "Reply-To:". According to the standard the case of letters should not matter, so you could actually use "reply-to" or "REPLY-TO". Even "rEpLy-tO" would word. But please do not change this as you never know what this might break at the recipient's side. One is is required in all cases, though, and that's the *space* after the colon. Don't miss that one!

Valid address!
Use a *valid address. Directing replies into oblivion is not nice. If you think that you must do this - please do not reply at all. When something goes wrong then more people could get involved. And creating trouble for more people is simply a no-no.

Use your name, too!
Put your name next to the address, too. Otherwise you'll get replies sent to your address only. You might think this is not a problem - but it is. Spammers (who send UCEs) do just that: They rarely send you mail with your name in the headers. So a missing name is a indicator for spams. By leaving out your name you therefore make other spammers. And your correspondents might even update there mail aliases from your mail which just pick up addresses from the Reply-To: line. When your name is missing then how will know later that "foo123barX@weirddomain" was you?

No redundant Reply-To: line!
Often I see people sending mails where the contents of the From: line equals the contents of the Reply-To: line. This is completel redundant and it might interfere with a Reply-To: line set eg by a mailing list server. But this is yet another problem of its own... ;-)


Summary

Reply-To: FirstName LastName <valid.address>

Sven Guckes http://learn.to/use-reply-to and http://remember.to/use-reply-to