How do I assign a value to a MailMessage ReplyTo property?

I want to set the ReplyTo value for a .NET MailMessage.

MailMessage.ReplyTo Property:

> ReplyTo is obsoleted for this type. > Please use ReplyToList instead which > can accept multiple addresses.

MailMessage.ReplyToList Property:

> Gets or sets the list of addresses to > reply to for the mail message.

But, ReplyToList is ReadOnly.

I've tried to use the MailMessage.Headers property like this:

mail.Headers.Add("Reply-To", "[email protected]");

as described here: System.Web.Mail, OH MY!

But, that doesn't seem to work.

How do I set the value(s) of the MailMessage's ReadOnly property ReplyToList?

ReplyToList is an instance of MailAddressCollection which exposes Add method.

To add a new address you can simply pass address as string

  message.ReplyToList.Add("[email protected]");

I like the array init syntax, which will call Add() for you.

var msg = new MailMessage("[email protected]", mailTo) {
    Subject = "my important message",
    Body = this.MessageBody,
    ReplyToList = { mailTo } // array init syntax calls Add()
};
mailClient.Send(msg);

You cannot say

message.ReplyToList = new MailAddressCollection();

To create a new collection. However, adding to the existing collection is what you want to do.

message.ReplyToList.Add(new MailAddress("[email protected]"));

My answer is not unlike the accepted answers already given. However, I felt it needed to be provided.

var fromEmail = new MailAddress("[email protected]", "Foo Bar");
var replyEmail = new MailAddress("[email protected]", "Foo Example");
var msgEmail = new MailMessage { From = fromEmail };
msgEmail.ReplyToList.Add( replyEmail );

I used the MailMessage.Sender property instead.

mail.Sender = new Mail.MailAddress("[email protected]");
mail.From = new Mail.MailAddress("[email protected]", "John Doe");

More info: MailMessage, difference between Sender and From properties

You need to add list of ReplyTo Addresses to ReplyToList by Add method :

            mail.Sender = new MailAddress(from, displayName);
            mail.From = new MailAddress(from, displayName);
            mail.ReplyToList.Add("[email protected]");

MailMessage.ReplyToList.Add("[email protected], [email protected], [email protected]");

Ref. https://docs.microsoft.com/en-us/dotnet/api/system.net.mail.mailaddresscollection.add?redirectedfrom=MSDN&view=netframework-4.8#overloads

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I expect that it is also possible to optionally include "friendly name" using the above approach, probably using this format: Jon Doe <[email protected]>

Refs.: https://askleo.com/why_are_email_addresses_sometimes_in_anglebrackets/, https://help.returnpath.com/hc/en-us/articles/220563147-What-is-a-Friendly-From-name-and-address-, https://wordtothewise.com/2014/12/friendly-email-addresses/.