次のように Rails を使用してメールを送信しています。
attachments["ticket.pdf"] = WickedPdf.new.pdf_from_string(render_to_body(pdf: "ticket", template: 'template' }))
これは Gmail ではうまく機能しますが、他のいくつかのクライアントでは、添付された pdf が表示されません。
ソースコードを見ると、mimeparts に問題があることがわかりました。
添付ファイルを yahoo や Thunderbird などの他のいくつかの電子メール クライアントで表示するのに苦労しています。送信された電子メールのソース コードを分析すると、ファイルの各部分で mimepart が同じであることがわかります。 .階層は（私が理解している限り）次のようでなければなりません：
multipart/mixed
multipart/alternative
multipart/related
text/html
image/png (e.g. for an inline attachment; pdf would be another good example)
text/plain
application/zip (e.g for an attachment--not inline)
これはhttps://github.com/jcoleman/mail_alternatives_with_attachmentsから抽出しました
以下は、電子メールのソースです (理解を深めるために、コンテンツの一部のみを抜粋しています)。
Delivered-To: someone@yahoo.com
Received: by 10.194.54.135 with SMTP id j7csp144091wjp;
Fri, 28 Sep 2012 10:55:03 -0700 (PDT)
Received: by 10.224.187.146 with SMTP id cw18mr18768052qab.35.1348854902751;
Fri, 28 Sep 2012 10:55:02 -0700 (PDT)
Return-Path: <somewhare@company.com>
Received: from mail-qa0-f46.company.com (mail-qa0-f46.company.com [209.85.216.46])
by mx.company.com with ESMTPS id c6si13006455qao.34.2012.09.28.10.55.02
(version=TLSv1/SSLv3 cipher=OTHER);
Fri, 28 Sep 2012 10:55:02 -0700 (PDT)
Received-SPF: pass (company.com: domain of somewhere@company.com designates 209.85.216.46 as permitted sender) client-ip=xx.xxx.xxx.xxx;
Authentication-Results: mx.company.com; spf=pass (company.com: domain of somwhere@company.com designates 209.85.216.46 as permitted sender) smtp.mail=somewhere@company.com; dkim=pass header.i=@company.com
Received: by mail-qa0-f46.company.com with SMTP id c26so105866qad.5
for <someone@company.com>; Fri, 28 Sep 2012 10:55:02 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=company.com; s=20120113;
h=date:from:reply-to:to:message-id:subject:mime-version:content-type
:content-transfer-encoding;
bh=nETVpMomUq0PkrNf9ScGjdaBPc5tYF0m1Rphx5FNS4c=;
b=I1ICSRRK10cdrqXxkNWmK5cLvXOqFpxXmzxNMlIVa8jh+4U1GwqwI1GZF7BRXh5FAU
wCyTzXfSkBrmn2cVGwUUiNEh956KT2ssWx37cQIb915lSp6rdIqflgQcF9yKwmtJoxDL
qO+nEVse7+Azi828zC7D6VV7ebAbmnr006KmppkH9bxILk+syiPKLvp4rZXAMIp0IFW8
nYZ2jY+n/ryduTSl0qDaBDCzVrky2eNwpqfJYizoYWIhxFuDmUWwaPpKzfWoxzT4b0+P
Mp/Ugv6iN1QyETJWbOfX4lpGezFzcaV7reZaBXLzcqUe1dc8elxFfWncsE0vozmFaj8m
z37Q==
Received: by 10.224.58.134 with SMTP id g6mr18690371qah.40.1348854902269;
Fri, 28 Sep 2012 10:55:02 -0700 (PDT)
Return-Path: <somwhere@company.com>
Received: from localhost.localdomain (company.com. [xx.xxx.xxx.xx])
by mx.company.com with ESMTPS id ck11sm13357478qab.17.2012.09.28.10.54.56
(version=TLSv1/SSLv3 cipher=OTHER);
Fri, 28 Sep 2012 10:55:00 -0700 (PDT)
Return-Path: <bounces1@somewhere.com>
Date: Fri, 28 Sep 2012 15:09:56 -0300
From: somewhere <somewhere@company.com>
Reply-To: someone@company.com
To: someone@company.com
Message-ID: <5065e7f4b41bf_a9e43fdbdd45a7601574c@megara.local.mail>
Subject: algun subject
Mime-Version: 1.0
Content-Type: multipart/alternative;
boundary="--==_mimepart_5065e7f4af345_a9e43fdbdd45a760153b9";
charset=UTF-8
Content-Transfer-Encoding: 7bit
----==_mimepart_5065e7f4af345_a9e43fdbdd45a760153b9
Date: Fri, 28 Sep 2012 15:09:56 -0300
Mime-Version: 1.0
Content-Type: text/plain;
charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Content-ID: <5065e7f4b0ead_a9e43fdbdd45a7601546@megara.local.mail>
********
texto cualquiera
********
----==_mimepart_5065e7f4af345_a9e43fdbdd45a760153b9
Date: Fri, 28 Sep 2012 15:09:56 -0300
Mime-Version: 1.0
Content-Type: text/html;
charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Content-ID: <5065e7f4b1d7d_a9e43fdbdd45a76015576@megara.local.mail>
<html xmlns=3D'http://www.w3.org/1999/xhtml'>
<html xml:lang=3D'en' xmlns=3D'http://www.w3.org/1999/xhtml'>
<head>
<meta content=3D'text/html; charset=3Dutf-8' http-equiv=3D'Content-=
Type'>
<title>somewhere</title>
<link href=3D'/assets/ev_classic_mailer.css' rel=3D'stylesheet' typ=
e=3D'text/css'>
<link href=3D'/assets/mailer_colors.css' rel=3D'stylesheet' type=3D=
'text/css'>
</head>
<body>
<table class=3D'mail-container-table'>
<tr>
<td class=3D'decoration' colspan=3D'3'></td>
</tr>
<tr>
<th background=3D'https://here.company.com/ass=
ets/mail/ev_classic_hd.png' class=3D'bcolor12 border header-01' colspan=3D=
'3'>
<h1>cogotudo</h1>
</th>
</tr>
</table>
</body>
</html>
</html>
----==_mimepart_5065e7f4af345_a9e43fdbdd45a760153b9
Date: Fri, 28 Sep 2012 15:09:56 -0300
Mime-Version: 1.0
Content-Type: text/html;
charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Content-ID: <5065e7f4b2ede_a9e43fdbdd45a76015666@megara.local.mail>
<html xmlns=3D"http://www.w3.org/1999/xhtml" style=3D"outline: 0; font-we=
ight: inherit; font-style: inherit; font-size: 100%; font-family: inherit=
; vertical-align: baseline; margin: 0; padding: 0; border: 0;">
<html xml:lang=3D"en" xmlns=3D"http://www.w3.org/1999/xhtml" style=3D"o=
utline: 0; font-weight: inherit; font-style: inherit; font-size: 100%; fo=
nt-family: inherit; vertical-align: baseline; margin: 0; padding: 0; bord=
er: 0;">
<head>
<meta content=3D'text/html; charset=3Dutf-8' http-equiv=3D'Content-=
Type'>
<title>somewhere</title>
<link href=3D'/assets/ev_classic_mailer.css' rel=3D'stylesheet' typ=
e=3D'text/css'>
<link href=3D'/assets/mailer_colors.css' rel=3D'stylesheet' type=3D=
'text/css'>
</head>
<body style=3D"outline: 0; font-weight: inherit; font-style: inherit;=
</body>
</html>
</html>
----==_mimepart_5065e7f4af345_a9e43fdbdd45a760153b9
Date: Fri, 28 Sep 2012 15:09:56 -0300
Mime-Version: 1.0
Content-Type: application/pdf;
charset=UTF-8;
filename=ticket.pdf
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename=ticket.pdf
Content-ID: <5065e7f43b81b_a9e43fdbdd45a760150c9@megara.local.mail>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----==_mimepart_5065e7f4af345_a9e43fdbdd45a760153b9--