analyzing-outlook-pst-for-email-forensics

name	analyzing-outlook-pst-for-email-forensics
description	Parse Microsoft Outlook PST and OST files using libpff and pst-utils to extract message content, headers, attachments, deleted items, and MAPI metadata, including recovery of items from the Recoverable Items folder. Use when conducting email forensic investigations, legal e-discovery, or incident response that requires reconstructing communication patterns or tracing message routing from Outlook archives.
domain	cybersecurity
subdomain	digital-forensics
tags	["email-forensics","pst","ost","outlook","mapi","email-headers","attachments","deleted-emails","libpff","eml-extraction"]
version	1.0
author	mahipal
license	Apache-2.0
nist_ai_rmf	["MANAGE-2.4","MANAGE-3.1","MEASURE-3.1"]
nist_csf	["RS.AN-03","DE.AE-02","RS.MA-01"]
mitre_attack	["T1114.001","T1564.008","T1070.008"]

Analyzing Outlook PST for Email Forensics

Overview

Microsoft Outlook PST (Personal Storage Table) and OST (Offline Storage Table) files are critical evidence sources in digital forensics investigations. PST files store email messages, calendar events, contacts, tasks, and notes in a proprietary binary format based on the MAPI (Messaging Application Programming Interface) property system. Forensic analysis of these files enables recovery of deleted emails (from the Recoverable Items folder), extraction of email headers for tracing message routes, analysis of attachments for malware or exfiltrated data, and reconstruction of communication patterns. Modern PST files use Unicode format with 4KB pages and can grow up to 50GB, while legacy ANSI format is limited to 2GB.

When to Use

• When investigating security incidents that require analyzing outlook pst for email forensics
• When building detection rules or threat hunting queries for this domain
• When SOC analysts need structured procedures for this analysis type
• When validating security monitoring coverage for related attack techniques

Prerequisites

• libpff/pffexport (open-source PST parser)
• Python 3.8+ with pypff or libratom libraries
• MailXaminer, Forensic Email Collector, or SysTools PST Forensics (commercial)
• Microsoft Outlook (optional, for native PST access)
• Sufficient disk space for extracted content

PST File Locations

Source	Path
Outlook 2016+ Default	%USERPROFILE%\Documents\Outlook Files*.pst
Outlook Legacy	%LOCALAPPDATA%\Microsoft\Outlook*.pst
OST Cache	%LOCALAPPDATA%\Microsoft\Outlook*.ost
Archive	%USERPROFILE%\Documents\Outlook Files\archive.pst

Analysis with Open-Source Tools

libpff / pffexport

# Export all items from PST file
pffexport -m all evidence.pst -t exported_pst

# Export only email messages
pffexport -m items evidence.pst -t exported_emails

# Export recovered/deleted items
pffexport -m recovered evidence.pst -t recovered_items

# Get PST file information
pffinfo evidence.pst

Python PST Analysis

import pypff
import os
 json
 hashlib
 email
 sys
 datetime  datetime
 collections  defaultdict


 :
    

     ():
        .pst_path = pst_path
        .output_dir = output_dir
        os.makedirs(output_dir, exist_ok=)
        .pst = pypff.file()
        .pst.(pst_path)
        .messages = []
        .attachments = []
        .stats = defaultdict()

     ():
        
        folder_name = folder.name  
        current_path =   folder_path  folder_name

         i  (folder.number_of_sub_messages):
            :
                message = folder.get_sub_message(i)
                msg_data = .extract_message(message, current_path)
                 msg_data:
                    .messages.append(msg_data)
                    .stats[] += 
             Exception  e:
                .stats[] += 

         i  (folder.number_of_sub_folders):
            :
                subfolder = folder.get_sub_folder(i)
                .process_folder(subfolder, current_path)
             Exception:
                

     () -> :
        
        msg_data = {
            : folder_path,
            : message.subject  ,
            : message.sender_name  ,
            : ,
            : (message.creation_time)  message.creation_time  ,
            : (message.delivery_time)  message.delivery_time  ,
            : (message.modification_time)  message.modification_time  ,
            : message.number_of_attachments > ,
            : message.number_of_attachments,
            : (message.plain_text_body  ),
            : (message.html_body  ),
        }

        
        headers = message.transport_headers
         headers:
            msg_data[] = 
            msg_data[] = (headers)
            
            parsed = email.message_from_string(headers)
            msg_data[] = parsed.get(, )
            msg_data[] = parsed.get(, )
            msg_data[] = parsed.get(, )
            msg_data[] = parsed.get(, )
            msg_data[] = parsed.get(, )
            msg_data[] = parsed.get_all(, [])

        
         j  (message.number_of_attachments):
            :
                attachment = message.get_attachment(j)
                att_data = {
                    : msg_data[],
                    : attachment.name  ,
                    : attachment.size,
                    : ,
                }
                .attachments.append(att_data)
                .stats[] += 
             Exception:
                

         msg_data

     ():
        
        att_dir = os.path.join(.output_dir, )
        os.makedirs(att_dir, exist_ok=)

        root = .pst.get_root_folder()
        ._save_attachments_recursive(root, att_dir, max_size_mb)

     ():
         i  (folder.number_of_sub_messages):
            :
                message = folder.get_sub_message(i)
                 j  (message.number_of_attachments):
                    att = message.get_attachment(j)
                     att.size  att.size < max_size_mb *  * :
                        name = att.name  
                        safe_name = .join(c  c.isalnum()  c      c  name)
                        path = os.path.join(att_dir, safe_name)
                        :
                            data = att.read_buffer(att.size)
                             (path, )  f:
                                f.write(data)
                         Exception:
                            
             Exception:
                

         i  (folder.number_of_sub_folders):
            :
                ._save_attachments_recursive(folder.get_sub_folder(i), att_dir, max_size_mb)
             Exception:
                

     () -> :
        
        root = .pst.get_root_folder()
        .process_folder(root)

        report = {
            : datetime.now().isoformat(),
            : .pst_path,
            : os.path.getsize(.pst_path),
            : (.stats),
            : .messages[:],
            : .attachments[:],
        }

        report_path = os.path.join(.output_dir, )
         (report_path, )  f:
            json.dump(report, f, indent=, default=)

        ()
        ()
        ()
         report_path

     ():
        .pst.close()


 ():
     (sys.argv) < :
        ()
        sys.exit()
    analyzer = PSTForensicAnalyzer(sys.argv[], sys.argv[])
    analyzer.generate_report()
    analyzer.close()


 __name__ == :
    main()