Last Modified
  2015-07-22 02:29:34 +0000
Requires
  - mail/fields/common/common_message_id

## Description

# In-Reply-To Field

The In-Reply-To field inherits from StructuredField and handles the In-Reply-To: header field in the email.

Sending in_reply_to to a mail message will instantiate a Mail::Field object that has a InReplyToField as it's field type. This includes all Mail::CommonMessageId module instance metods.

Note that, the message_ids method will return an array of message IDs without the enclosing angle brackets which per RFC are not syntactically part of the message id.

Only one InReplyTo field can appear in a header, though it can have multiple Message IDs.

## Examples:

    mail = Mail.new
    mail.in_reply_to = '<F6E2D0B4-CC35-4A91-BA4C-C7C712B10C13@test.me.dom>'
    mail.in_reply_to    #=> '<F6E2D0B4-CC35-4A91-BA4C-C7C712B10C13@test.me.dom>'
    mail[:in_reply_to]  #=> '#<Mail::Field:0x180e5e8 @field=#<Mail::InReplyToField:0x180e1c4
    mail['in_reply_to'] #=> '#<Mail::Field:0x180e5e8 @field=#<Mail::InReplyToField:0x180e1c4
    mail['In-Reply-To'] #=> '#<Mail::Field:0x180e5e8 @field=#<Mail::InReplyToField:0x180e1c4

    mail[:in_reply_to].message_ids #=> ['F6E2D0B4-CC35-4A91-BA4C-C7C712B10C13@test.me.dom']