How to parse text file (.eml) to get index of line, that contains Subject, From field, and base64 decoded Body

Question

Hello, Dear Colleagues.
Help me please with next deal.
As input I have .eml file:
x-sender: [email protected]
x-receiver: ***************************
Received: from ***** with Microsoft SMTPSVC(7.5.7601.17514);
Fri, 20 Mar 2015 12:43:03 +0200
In-Reply-To: <********@LocalDomain>
To: *****************************
Bcc:
Subject: Incident ID#: 117 Something wrong, something right, something missing
Message-ID: <*****************************@LocalDomain>
From: [email protected]
Date: Fri, 20 Mar 2015 12:42:55 +0200
Content-Type: multipart/related; boundary="=_related ********************"
References: <*******************************C@LocalDomain>
MIME-Version: 1.0
X-KeepSent: ****************************; name=$KeepSent; type=4
X-Mailer: Lotus Notes Release 8.5.2FP3 July 11, 2011
X-Disclaimed: 54023
Return-Path: [email protected]
X-OriginalArrivalTime: 20 Mar 2015 10:43:03.0590 (UTC) FILETIME=[A48E9C60:01D062FA]
--=_related **********************=
Content-Type: multipart/alternative; boundary="=_alternative &**************"
--=_alternative ******************
Content-Type: text/plain; charset="KOI8-R"
Content-Transfer-Encoding: base64
U29tZXRoaW5nIHdyb25nLCBzb21ldGhpbmcgcmlnaHQsIHNvbWV0aGluZyBtaXNzaW5nDQpTb21l
dGhpbmcgYmxhY2ssIHNvbWV0aGluZyBsaWdodCwgc29tZXRoaW5nIGRpZmZlcmVudA0KRG9uJ3Qg
eW91IGV2ZXIgZmVlbCB5b3UgbmVlZCB0byBzcGVhayB0byBtZSB0aGF0IHdheT8NClNvbWV0aGlu
ZyBibGFjaywgc29tZXRoaW5nIGxpZ2h0LCBzb21ldGhpbmcgZGlmZmVyZW50DQpTb21ldGhpbmcg
d3JvbmcsIHNvbWV0aGluZyByaWdodCwgc29tZXRoaW5nIG1pc3NpbmcNCkRvbid0IHlvdSBldmVy
IGZlZWwgeW91IG5lZWQgdG8gc3BlYWsgdG8gbWUgdGhhdCB3YXk/IA==--=_alternative ******************
Content-Type: text/plain; charset="KOI8-R"
Content-Transfer-Encoding: base64
Because position of lines changes due to email type, as output I want to get:
1). index of line that contains: Subject, i.e. "Subject: Incident ID#: 117 Something wrong, something right, something missing"
2). index of line that contains "From", i.e. "From: [email protected]"
3). base64 - decoded text (body of email)
Thanks for your help.
Have a nice day.

Answer 1

jrv,
your script, unfortunately, always return "String not found".
Because you file is probably not constructed the same as the copy you posted.  I was just showing you how.  You will need to adjust to the actual file.
Outlook can open and convert  EML files. 
¯\_(ツ)_/¯