<#
.SYNOPSIS
zo3検証ツール 簡易MIMEメール作成スクリプト
New-MimeMessage.ps1
.DESCRIPTION
指定したヘッダ情報・本文・添付ファイルから RFC 2822 準拠の EML ファイルを生成する。
生成した EML は curl の --upload-file で SMTP 送信に使用できる。
検証環境・クローズド環境での使用を前提とする。
.PARAMETER From
送信者アドレス。例: user1@example.test
.PARAMETER To
宛先アドレス（複数指定可）。例: user2@example.test, user3@example.test
.PARAMETER Subject
件名。日本語可（RFC2047 Base64 エンコード）。
.PARAMETER Body
本文。日本語可（UTF-8 / 8bit）。
.PARAMETER Attachments
添付ファイルパスの配列（省略可）。日本語ファイル名可（RFC2231 エンコード）。
.PARAMETER OutFile
出力する EML ファイルパス。デフォルト: mail.eml
.EXAMPLE
.\New-MimeMessage.ps1 -From user1@example.test -To user2@example.test `
-Subject "テスト" -Body "本文" -OutFile test.eml
.EXAMPLE
.\New-MimeMessage.ps1 -From user1@example.test -To user2@example.test `
-Subject "添付テスト" -Body "本文" `
-Attachments @("C:\tmp\資料.pdf", "C:\tmp\image.png") -OutFile attach.eml
.NOTES
対応エンコード : Subject=RFC2047 B, ファイル名=RFC2231, 本文=UTF-8/8bit
非対応 : HTML メール, multipart/alternative, DKIM 署名, CC/BCC ヘッダ自動付与
送信例 :
curl.exe --url smtp://mailserver:25 `
--mail-from user1@example.test `
--mail-rcpt user2@example.test `
--upload-file test.eml
MIT License
Copyright (c) 2026 yoshio@zo3
#>
param(
[string]$From,
[string[]]$To,
[string]$Subject,
[string]$Body,
[string[]]$Attachments = @(),
[string]$OutFile = "mail.eml"
)
# ===== 基本 =====
$CRLF = "`r`n"
# ===== RFC2047 Subject =====
function Encode-Subject( $string ) {
$bytes = [System.Text.Encoding]::UTF8.GetBytes( $string )
$b64data = [Convert]::ToBase64String( $bytes )
return "=?UTF-8?B?${b64data}?="
}
# ===== Base64（76文字折返し）=====
function To-Base64Lines( $bytes ) {
$b64data = [Convert]::ToBase64String( $bytes )
return ( ${b64data} -split "(.{1,76})" | Where-Object { $_ }) -join $CRLF
}
# ===== RFC2231 filename* =====
function Encode-RFC2231( $string ) {
$bytes = [System.Text.Encoding]::UTF8.GetBytes( $string )
$enc = ""
foreach ( $byte in $bytes ) {
if (
( $byte -ge 0x30 -and $byte -le 0x39 ) -or
( $byte -ge 0x41 -and $byte -le 0x5A ) -or
( $byte -ge 0x61 -and $byte -le 0x7A ) -or
$byte -in 0x2D, 0x2E, 0x5F, 0x7E
) {
$enc += [char]$byte
}
else {
$enc += "%" + $byte.ToString( "X2" )
}
}
return "UTF-8''$enc"
}
# ===== Date / Message-ID =====
$now = Get-Date
#$dateStr = $now.ToString("ddd, dd MMM yyyy HH:mm:ss K", [System.Globalization.CultureInfo]::InvariantCulture)
$tz = $now.ToString("zzz").Replace(":", "")
$dateStr = $now.ToString("ddd, dd MMM yyyy HH:mm:ss", [System.Globalization.CultureInfo]::InvariantCulture) + " $tz"
$domain = ($From -split "@")[-1]
$msgid = "<" + [guid]::NewGuid().ToString() + "@$domain>"
# ===== boundary =====
$boundary = "----=_Boundary_" + [guid]::NewGuid().ToString("N")
# ===== ヘッダ =====
$headers = @()
$headers += "Date: $dateStr"
$headers += "Message-ID: $msgid"
$headers += "From: $From"
$headers += "To: " + ($To -join ", ")
$headers += "Subject: " + ( Encode-Subject $Subject )
$headers += "MIME-Version: 1.0"
if ($Attachments.Count -gt 0) {
$headers += "Content-Type: multipart/mixed; boundary=""$boundary"""
}
else {
$headers += "Content-Type: text/plain; charset=UTF-8"
$headers += "Content-Transfer-Encoding: 8bit"
}
# ===== 本文 =====
$bodyLines = @()
# 修正（本文取り込み前に正規化）
$Body = $Body -replace "`r`n", "`n" -replace "`n", $CRLF
if ( $Attachments.Count -eq 0 ) {
$bodyLines += $Body
}
else {
# 本文パート
$bodyLines += "--$boundary"
$bodyLines += "Content-Type: text/plain; charset=UTF-8"
$bodyLines += "Content-Transfer-Encoding: 8bit"
$bodyLines += ""
$bodyLines += $Body
# 添付
foreach ( $file in $Attachments ) {
$bytes = [System.IO.File]::ReadAllBytes( $file )
$name = [System.IO.Path]::GetFileName( $file )
# ASCIIフォールバック
$nameAscii = $name -replace '[^\x20-\x7E]', '_'
# RFC2231
$name2231 = Encode-RFC2231 $name
$bodyLines += ""
$bodyLines += "--$boundary"
$bodyLines += "Content-Type: application/octet-stream; name=""$nameAscii"""
$bodyLines += "Content-Transfer-Encoding: base64"
$bodyLines += "Content-Disposition: attachment; filename=""$nameAscii""; filename*=$name2231"
$bodyLines += ""
$bodyLines += (To-Base64Lines $bytes)
}
# 終端
$bodyLines += ""
$bodyLines += "--$boundary--"
}
# ===== 結合 =====
$all = ( $headers -join $CRLF ) + $CRLF + $CRLF + ( $bodyLines -join $CRLF )
# ===== 出力（CRLF維持）=====
#[System.IO.File]::WriteAllText( $OutFile , $all , [System.Text.Encoding]::ASCII)
[System.IO.File]::WriteAllBytes($OutFile, [System.Text.Encoding]::UTF8.GetBytes($all))