Email Archiving

Email archiving is a system for preserving email communications in a secure, indexed, and retrievable digital format. This archiving mechanism acts as a digital safety net that captures every message, attachment, and thread in a centralized repository. Organizations typically deploy email archiving solutions for one or more of the following reasons:

• Regulatory compliance: Many industries mandate retention periods for emails (e.g., financial services, healthcare), requiring tamper-proof records to avoid fines or legal exposure.
• Intellectual property protection: Secures sensitive IP in tamper-proof archives with granular access controls, ensuring only authorized users can view or modify proprietary data.
• Business continuity and disaster recovery: Maintains off-site, encrypted copies of archives for instant recovery during outages or cyber-attacks and bypasses compromised primary systems.
• Litigation readiness: Courts increasingly demand email evidence during disputes; archiving ensures organizations can swiftly produce accurate records.
• Knowledge retention: Preserving institutional knowledge embedded in email threads protects against disruptions from employee turnover or system failures.
• Infrastructure efficiency: Archiving emails reduces strain on primary email servers and improves performance while lowering long-term storage costs.

With 60% of business-critical data now stored exclusively in email systems, archiving has become indispensable for safeguarding data integrity and ensuring rapid access during audits, investigations, or disaster recovery scenarios.

Organizations are generating more data—and more kinds of data—every day. Managing an email archiving system in a way that is compliant, cost-effective, and efficient has never been more complicated.

To get the most out of their email archiving investments, organizations should look for these features as part of email archiving best practices:

Good performance and user experience

The ideal email archiving system provides a centralized, searchable repository that gives users access to historical data. At the user level, it should be simple and intuitive, with a familiar user experience that fits the organization’s workflow and keeps employees productive. And search performance should be fast and accurate, no matter how large the archive grows. At the organizational level, it should help IT, compliance, and legal teams reduce the cost and complexity of managing and monitoring today’s exploding data volumes.

High fidelity and data quality

To demonstrate the chain of custody and preserve every message that organizations need, email archiving best practices dictate that the archive should be failsafe. Consider an email archiving solution that guarantees no message is lost, even if the network goes down. Insist that the cloud archiving vendor can prove that nothing is removed from the journaling mailbox until it is safely in the archive. The solution should also provide complete reporting and a transparent, unalterable audit trail that lets the organization demonstrate that it has met all retention, chain-of-custody, and legal-hold requirements.

Data security

If the archived data isn’t safe, then organizations risk non-compliance. Any data that leaves the environment should always be encrypted to keep it secure. Consider a cloud archiving solution that protects in transit and at rest in the cloud archive infrastructure. The encryption key should be the organization’s alone—not shared with the cloud archive provider—so that it retains full control over who can access archival data. Data centers used to house the cloud archive should be SSAE-16 SOC 2 Type II certified—not just for the physical facilities, but for the service itself.

Comprehensive audit trails

Audit logs must track every action, from access attempts to policy changes, to demonstrate compliance during regulatory inspections. Immutable logs with timestamped entries provide irrefutable evidence of data handling and compliance management practices. For example, a major hospital system could use these trails to prove PHI was accessed only by authorized personnel during an audit.

Robust email security

A secure email archive safeguards sensitive communications from unauthorized access, breaches, or tampering. Prioritize end-to-end protection solutions that encrypt data both during transmission and while stored. Organizations should retain exclusive control over their encryption keys, helping prevent third parties from accessing archived content without explicit authorization. Additionally, align archiving practices with zero-trust principles and choose email security vendors that adhere to rigorous security standards.

Independent backup systems

Maintain geographically isolated backups of archives, separate from primary storage. For example, pair a cloud archive (e.g., Microsoft 365) with an on-premises cold storage backup that is updated weekly. This redundancy mitigates risks like cloud provider outages or ransomware encryption. Even cloud-based archives are vulnerable to sync errors or accidental deletions. Independent backups ensure continuity if primary systems fail.

In years past, “storage optimization was a top reason for organizations to archive email,” says Shawn Aquino, Proofpoint’s Manager of Product Marketing. But today, “archiving emails have evolved well beyond storage optimization, driven in large part by the adoption of cloud computing, data privacy mandates and more,” Aquino adds.

By transforming fragmented communication into a structured strategic resource, email archiving empowers organizations to protect stakeholder interests, streamline workflows, and drive informed decision-making. Below are key areas where archiving delivers transformative value:

Enabling Regulatory Compliance

Email archiving automates adherence to industry-specific mandates like GDPR, HIPAA, or FINRA by enforcing retention periods and audit trails. Systems classify emails based on content (e.g., financial records, patient data) and apply encryption or access restrictions to meet strict privacy standards. “For companies subject to FINRA regulation, for example, increased oversight and mitigating compliance risks are two significant reasons why to archive email (and sometimes other digital communications),” Aquino says.

Streamlining Litigation and Investigation Readiness

The degree to which your people, processes, automatically redact personally identifiable information (PII) and monitor for suspicious access patterns, shrinking the pool of exploitable data.

Accelerating Access to Legacy Email

Employees waste hours weekly searching outdated inboxes or disconnected PST files. Archiving centralizes decades of emails into a unified, searchable repository compatible with modern platforms like Microsoft 365. Teams retrieve legacy contracts, client agreements, or project notes in seconds using natural language queries, bypassing fragmented storage systems.

Optimizing Backup and Recovery

“Are you able to execute retention policies on your email? In other words, can you keep emails for a prescribed amount of time, and then delete them afterwards? I ask because some vendors force you to implement a legal hold on all user data to protect against deliberate or accidental deletions, thus undermining the notion of a data retention policy,” Aquino highlights.

Traditional backups often lack search functionality and retention controls, making disaster recovery slow and inefficient. Archiving systems store emails in geographically redundant cloud environments, which enable enterprises to restore critical communications within minutes during outages or ransomware attacks. Unlike live servers, archives remain isolated from network breaches, ensuring data remains accessible even if primary systems are compromised.

Aligning Departments Across the Organization

Legal, IT, HR, and leadership teams often clash over data access priorities. A centralized archive serves as a neutral platform where legal teams apply holds, IT manages storage costs, and HR retrieves historical employee communications – all without conflicting workflows. This alignment reduces interdepartmental friction and ensures consistent data governance.

While email archives have traditionally been stored on magnetic tape and other low-cost media, the cloud is an increasingly popular email archiving option due to falling costs, greater efficiencies, and added capabilities vs. on-premises archiving. The trend will only accelerate as more and more data originates from and lives in the cloud.

Other companies are moving their archives to cloud-based email archiving to shrink their data and infrastructure footprint. Such a move can lower costs because cloud services enjoy IT economies of scale that even most large enterprises can’t match. The move can also improve security and performance. Retrieving data for audits and legal requests from a cloud-based email archive is usually much easier and faster than with on-premises vaults. For companies already moving their email and collaboration infrastructure to Office 365, the choice is even clearer—even the best on-premises compliance archives can’t archive cloud-based content efficiently.

Compared to aging on-premises, cloud-based email archiving is often less expensive, easier to manage, and more reliable. But the switch can seem daunting, and it comes with its own challenges. For many organizations that use legacy email archiving software and years of data archives to manage, a hybrid approach might make more sense.

Migrating an email archive to the cloud costs time, money, and resources. To streamline the process and reduce the risk of data loss, organizations should consider an email archive migration strategy that fits their goals, needs, and resources.

Here are four approaches to consider:

• Move all the data.
• Put new data in the cloud, keep old data in an existing archive.
• Migrate all critical data.
• Migrate data that falls within your retention policy.

Each option has pros and cons, and no single approach is best for every organization. Email archiving has become increasingly nuanced based on industry demands and technological innovation. Below is an expanded analysis of archival approaches, including hybrid, PST, and specialized models:

Hybrid Email Archiving

Hybrid solutions blend on-premises infrastructure with cloud storage, often keeping recent data locally for quick access while offloading older records to cost-effective cloud repositories. This model suits organizations transitioning from legacy systems or managing mixed environments (e.g., partially migrated to Office 365).

For example, financial firms might retain sensitive client communications on-premises for compliance while archiving routine correspondence in the cloud. Hybrid setups reduce upfront migration costs but require careful synchronization to avoid data silos or retention policy gaps.

Mailbox-Level Archiving

Mailbox-level archiving targets specific users or departments, such as executives or legal teams, whose communications demand prioritized retention. Unlike organization-wide solutions, this approach allows granular control over high-value data.

For instance, Microsoft’s In-Place Archive in Exchange Server automatically moves older emails from primary mailboxes to dedicated archive folders, reducing server load while preserving accessibility. However, decentralized management can lead to inconsistent policies, requiring oversight to align with broader compliance goals.

PST-Based Archiving

Personal Storage Table (PST) files enable users to manually archive emails locally, often to free up mailbox space. While simple, PSTs pose significant risks:

• Data loss: Files corrupt easily and lack centralized backup, exposing organizations to unrecoverable data loss.
• Compliance gaps: Decentralized storage complicates e-discovery, as legal teams must manually search scattered files.
• Security vulnerabilities: PSTs stored on endpoints are susceptible to theft or ransomware.

Many enterprises now phase out PSTs in favor of cloud or hybrid systems that centralize control and automate retention.

Journaling Archiving

Journaling captures a copy of every email traversing an organization’s servers, creating an immutable record for compliance or audits. Common in regulated industries like healthcare or finance, journaling archives store data in WORM (Write Once, Read Many) formats to prevent tampering. These systems often integrate with e-discovery tools to streamline legal requests but require significant storage capacity due to their all-encompassing scope.

Compliance-Focused Archiving

Tailored for industries like healthcare (HIPAA) or finance (SOX), compliance archives feature automated retention policies, audit trails, and role-based access. For example, a HIPAA-compliant system might encrypt emails containing PHI and log every access attempt. These solutions prioritize demonstrable adherence over flexibility, often sacrificing user-friendly interfaces for rigorous security controls.

Organizations across industries face stringent email archiving mandates to meet legal, financial, and sector-specific obligations. These rules apply to organizations beyond traditionally regulated sectors like finance or healthcare, as they can impact businesses of all sizes. Regulatory compliance often requires organizations to collect, monitor, retain, and produce these records on demand.^[1] Below is an expanded overview of critical regulations and their implications:

FINRA & SEC (Financial Sector)

Financial institutions must retain broker-dealer communications for 3–6 years under FINRA guidelines, while SEC Rule 17a-4 mandates a six-year retention period with immediate accessibility for the first two years. Emails must be stored in WORM format to prevent tampering, deletion, or edits. Compliance officers are required to supervise archives, ensuring that retention policies align with legal holds during investigations.

HIPAA (Healthcare)

Healthcare providers and insurers must retain PHI-containing emails for six years, alongside encryption and role-based access controls to safeguard patient data. Audit trails tracking access or modifications are mandatory, and records must be retrievable within 30 days for patient requests or audits. Violations, such as unauthorized disclosures, incur average fines of $1.5 million per incident, emphasizing the need for secure, compliant archiving.

SOX (Publicly Traded Companies)

The Sarbanes-Oxley Act requires publicly traded companies to retain financial records, employee communications, and audit trails for seven years after employment termination or the relevant event. Under SOX compliance, emails must be stored in non-rewritable formats, with third-party auditing capabilities to verify integrity. Non-compliance risks include delisting from stock exchanges, criminal charges for executives, and multimillion-dollar fines.

GDPR (General Data Protection Regulation)

The GDPR applies to any organization handling EU citizen data, mandating “data minimization” to retain emails only as long as necessary. Individuals may request erasure of personal data, requiring archives to support granular deletion unless exempted by legal holds. Penalties have reached €20 million or 4% of global revenue, making GDPR a top priority for multinational firms.

Additional Regulations

The Gramm-Leach-Bliley Act (GLBA) enforces seven-year retention for customer communications in financial services, while the Federal Rules of Civil Procedure (FRCP) demand rapid e-discovery capabilities for litigation. State laws, such as California’s 10-year retention for specific business records, add further complexity.

Compliance Strategies

Organizations adopt immutable storage solutions like WORM or blockchain-backed archives to prevent tampering. Automated retention policies classify emails by content (e.g., invoices, contracts) and apply deletion rules, while legal holds suspend these policies during audits or disputes. Audit trails log access and modifications, effectively providing evidence of compliance during regulatory inspections.

With Office 365 built-in archive comes with built-in archiving for end-user mailboxes. It’s a seamless, integrated experience that’s easy to use. But it’s meant for end-users, not IT departments.

With Office 365’s built-in archive, users can easily archive and find old emails. But without additional services, administrators, auditors, and legal teams can’t adequately archive, search, and supervise content across the enterprise.

With Office 365’s native archiving features, enterprise-wide email searches are difficult. Supervisory reviews are slow. And compliance policies can be applied to only a limited set of content. That leaves out a wide range of employee communication outside the Microsoft ecosystem, such as social media and instant messaging.

In many ways, the native archiving features of Gmail are even more limited.

For compliance, e-discovery, and corporate governance, most companies need a true enterprise-class email archiving solution that augments the platform’s native mailbox archiving features.

Deploying an effective email archiving strategy begins with aligning technical infrastructure, compliance requirements, and user needs. Prioritize cloud-based systems for scalability and cost efficiency, but verify they offer robust encryption, audit trails, and granular access controls to meet legal and security standards.

Proofpoint’s email archiving solutions simplify implementation while addressing critical business needs. With military-grade encryption and unique customer-controlled keys, it ensures data integrity and compliance across industries. For larger enterprises, Proofpoint offers advanced e-discovery tools, AI-driven search, and cross-regional policy enforcement, enabling rapid response to litigation or audits.

Learn more about how Proofpoint’s archiving solutions balance compliance, security, and usability by downloading our Essentials Email Archive data sheet or get in touch to learn more.

[1] Osterman Research. “Strategies for Archiving in Hybrid Environments.”