Top 10 Email Server Software: Features & Pricing in 2025

There are two main use cases for email servers. If you are looking for:

• A solution for sending outbound transactional emails (e.g., for marketing or customer service), which are automated and system-generated emails triggered by user actions. Check out transactional email providers.
• Email server for businesses and organizations to manage high volume email communications while offering more control, security, and customization, then check out email software.

Top 5 transactional email providers

Sorting: The list ranks providers, with sponsored entries shown first along with their respective links. All non-sponsored providers are listed in order of the total number of B2B user reviews collected from G2 and Capterra.

Pricing details and feature information were obtained directly from each vendor’s official website.

Vendor selection criteria: Only vendors with a minimum of 20 verified B2B reviews on platforms like Capterra and G2 were considered for this list.

Compare transactional email providers: Features

Top 5 email software

*These providers focus on email hosting and collaboration rather than directly offering transactional email services. For transactional emails, integrations with additional platforms or services are necessary.

** The data shows the total average rating and number of reviews for Microsoft 365.

Sorting in the above table: The table is organized primarily by the number of B2B reviews gathered from review sites such as G2 and Capterra. Information on pricing, deployment, and product features has been sourced directly from the vendors’ official sites.

Vendor Selection Criteria

We refined our shortlist using specific criteria:

1. Number of reviews: Vendors were prioritized if they had at least 100 public and verified B2B reviews, as a higher volume of such reviews signals a strong foothold in the transactional email server market.
2. Server protocols: We included software supporting a hybrid server protocol with both outgoing and incoming server capabilities. 

Compare email software: Deployment, focus & features

What is an email server?

An email server is a computer system responsible for sending, receiving, and storing electronic mail. It plays a central role in email communication by facilitating the transfer of messages between users and across networks.

Whether managing internal mail for a business or supporting millions of accounts for an email provider, the email server ensures reliable handling of incoming and outgoing emails.

Below are the essential features and functions of a modern email server:

Mailbox management

The server stores and organizes messages for each account. It allows users to access their inbox and folders via email clients or through a webmail interface. This supports mail access from mobile devices, desktop mail software, and browsers.

Protocol support

A standard email server relies on three core protocols:

• Simple Mail Transfer Protocol (SMTP server) for sending and routing outgoing mail
• Internet Message Access Protocol (IMAP server) and Post Office Protocol (POP) for retrieving new messages

These protocols work together to ensure messages reach the recipient’s mail server and are retrievable by the user through their chosen email client or mail interface.

Security measures

To protect sensitive data and maintain confidentiality, mail servers implement multiple layers of security. These include encryption through TLS/SSL, as well as authentication methods such as SPF, DKIM, and DMARC, to verify that outgoing emails originate from trusted sources.

Additional protections such as two-factor authentication and monitoring for active attacks help prevent unauthorized access, especially when users log in from different devices or locations.

Spam filtering

Email servers apply spam protection to detect and block unsolicited or malicious messages. These systems often include customizable mail filter rules and Bayesian filtering to maintain inbox integrity. Spam filtering helps distinguish legitimate communications from potential threats or junk mail.

Data backup and recovery

To protect against loss, modern email hosting platforms perform automated backups. These include both on-site and cloud-based backups. The ability to recover deleted messages or restore a mailbox is a critical feature in business environments, especially when handling regulatory compliance or sensitive communications.

Many email server solutions include automated DNS configuration and backup capabilities, making them ideal for smaller organizations seeking a self-hosted mail server.

Address resolution and routing

When users send emails, the server resolves the domain portion of the recipient’s address using DNS records. This ensures the message is directed to the correct recipient’s mail server. Accurate handling of vital DNS records, such as MX, SPF, and DKIM, is essential for successful email deliverability.

User authentication and access control

Only authorized users can access their accounts and send emails. Authentication mechanisms, password policies, and device-based controls prevent account compromise. This is particularly important in multi-user environments where messages must be isolated between accounts.

Scalability

Email servers scale based on demand. A mail server may support a single domain for a small organization or serve as a comprehensive solution for large-scale email providers.

Server software must accommodate a variety of mail server types and deployment models, ranging from local IMAP servers to cloud-hosted platforms.

Integration with other services

Many platforms offer calendar synchronization, task management, and contact integration, which enhance the user experience by centralizing communication and scheduling within a single interface.

Customizability and configuration

Administrators can configure features such as auto-responders, alias addresses, and forwarding rules to fit specific needs. Some servers support open source server software that can be tailored extensively, while others offer more managed setups with preset options.

AI-driven email infrastructure

Recent advancements have introduced AI tools into email infrastructure. These tools enhance spam filtering, detect compromised accounts, and improve mail deliverability.

On the other hand, attackers may utilize AI to craft more targeted phishing messages and evade traditional detection, necessitating the continuous adaptation of security measures.

Compliance with evolving privacy regulations

Changes in privacy laws, such as updates to GDPR and regional data governance rules, impact how email servers store and process messages. Server configurations now require stricter logging, encryption of sensitive data, and explicit user consent for marketing-related emails.

Innovation in email protocols

While the standard protocol stack (SMTP, IMAP, POP) remains widely used, early-stage alternatives, such as SHARP (Self-Hosted Address Routing Protocol), have emerged.

SHARP proposes a more modern JSON-based protocol for sending and receiving mail, but is currently limited to environments where both the sender and recipient use compatible server software.

Email server deployment: cloud vs on-premises

When selecting the right solution, it is crucial to determine whether cloud-based or on-premises services better meet your needs and expectations.

Cloud-based email servers provide a hosted solution that minimizes the need for internal IT management and infrastructure, offering:

• Scalability,
• Ease of access,
• A subscription-based cost model that is suitable for businesses seeking flexibility and minimal upfront investment.

On the other hand, on-premises email servers offer organizations:

• Full control over their email infrastructure,
• Data security and compliance,
• A higher initial investment in hardware,
• Ongoing management responsibilities extend beyond cloud-based services.

In short, cloud-based solutions offer advantages in accessibility and ease of scaling, while on-premises setups provide more control and customization options.

Shared or dedicated email server?

In some cases, businesses opt to use private email servers and mail server software to manage their email operations, giving them exclusive control over both incoming and outgoing emails. These servers offer:

• more control over email server hardware, email server software, and server space
• customization of security measures, spam filtering, and authentication protocols.

Businesses that utilize their servers can ensure that their email data and email communications are more secure and efficient, with advanced features such as spam protection and enhanced security.

In contrast, shared email servers are commonly managed by third-party providers, where multiple users share the same email infrastructure.

While shared servers offer lower costs, they come with limited control, and users rely on the third-party provider for security measures and spam filters.

This means that email deliverability and email data security can be more vulnerable to spam and malicious emails, potentially affecting email communications across multiple devices.

A dedicated mail server typically requires more technical expertise and incurs higher setup and maintenance costs. Still, it allows for complete control over SMTP server configurations, mail transfer agent (MTA) settings, and other elements of email server infrastructure. This level of control ensures that businesses:

• Can manage incoming and outgoing traffic.
• Configure DNS settings.
• Integrate advanced security measures to protect sensitive data and email messages.

How to decide?

For businesses that prioritize the security of their email operations and the protection of sensitive information, having dedicated email servers is highly recommended to ensure seamless email delivery and meet the demands of government agencies or organizations handling sensitive data.

On the contrary, shared email servers with limited control may be more suitable for personal use or smaller businesses that have less need for advanced security and require less control over their email communications.

Email server processes

Email servers manage the sending, receiving, and storing processes of email messages over the internet. These processes involve multiple steps and components, including Mail Transfer Agents (MTAs), Mail Delivery Agents (MDAs), and Mail User Agents (MUAs).

Creating and sending emails

• Composing an email: The process begins with a user creating an email using the email client (MUA), such as Microsoft Outlook, Yahoo Mail, Apple Mail, or a web-based service like Gmail.
• Client connecting to SMTP Server: The email client connects to the outgoing mail server using the Simple Mail Transfer Protocol (SMTP), which is responsible for sending emails.

Email routing

• Email Processing with SMTP Server: The SMTP server checks the email’s recipient address to determine where the email should be sent.
• DNS query for recipient’s server: The SMTP server queries a DNS server to find the Mail Exchange (MX) records for the recipient’s domain. The process enables the SMTP server to identify which incoming mail server the email will be sent to.
• Sending to recipient’s SMTP server: The sender’s SMTP server connects to the recipient’s SMTP server and transmits the email. If the recipient’s server is unavailable, the sender’s server will queue the email and try again later.

Receiving emails

• Recipient’s SMTP server receives email: Once the email reaches the recipient’s SMTP server, it’s handed off to a Mail Delivery Agent (MDA). The MDA is responsible for depositing the email into the appropriate mailbox on the server.
• Email storage: The email remains stored on the recipient’s email server until the recipient’s email client requests it.

Accessing emails

Lastly, the email client connects to the incoming mail server using: 

• The Post Office Protocol (POP3) or 
• The Internet Message Access Protocol (IMAP). 

Then, the email client retrieves the email from the server, thus allowing the recipient to read it.

Categories of email server solutions

Email servers can be categorized as either outgoing (SMTP servers), incoming (IMAP/POP servers), or hybrid servers that support all three protocols.

Email software 

Email software utilizes hybrid servers with capabilities for sending, receiving, and storing email communications in large volumes. These solutions can be open-source, cloud-based, or on-premises. They provide a foundation for email delivery and management.

With its integration capabilities for both web and mobile devices, including shared calendars, task management, contact management, and document sharing, email software can enhance teamwork and support project management processes.

Most email software allows users to access and respond to emails offline, enabling them to read and reply to emails even without an internet connection.

Transactional email providers

Transactional email providers integrate SMTP servers to enable the sending of system-generated emails to individuals based on specific actions or events. These messages facilitate direct communication by delivering information relevant to a user’s interaction with a website, application, or service. Unlike promotional emails, these are functional, time-sensitive, and expected by the recipient.

Trigger-based communication

Transactional email systems automate the sending of emails triggered by user behavior. Common examples include:

• Order confirmations
• Account activity alerts (e.g., delivery rates, clicks, bounces, spam complaints)
• Password resets
• Account activation links
• Privacy policy updates
• Shipping confirmations and tracking
• Payment receipts and invoices
• Two-factor authentication (2FA) codes

These messages are generated automatically and are tied to the recipient’s specific actions.

Figure 1: An example of password reset emails from Spotify.¹

Personalized messages with high visibility

Transactional emails are personalized and contain information required to complete or confirm a transaction. Since users generally anticipate these messages, they tend to exhibit high open and click-through rates. This enhances their reliability for delivering critical content such as sensitive data and system credentials.

API and SMTP integration

Transactional email providers support integration via RESTful APIs and SMTP relay services. API-based delivery is widely used in web and mobile applications for sending transactional messages in real time.

SMTP relay enables outgoing emails to be transferred across mail servers, ensuring proper routing to the recipient’s mail server using DNS records. This is essential for communication between systems using different email providers or mail server types.

SMTP relay process

When a message is generated, the sending SMTP server performs a DNS lookup based on the recipient’s email domain to identify the appropriate destination mail server.

The message is then routed across intermediate servers, arriving at the recipient’s inbox if accepted by the destination server.

This process is subject to domain-based authentication checks such as SPF, DKIM, and DMARC, which are now required by most major providers for email deliverability compliance.

Deliverability monitoring and authentication

Due to stricter enforcement policies by platforms like Gmail and Microsoft, transactional email systems must support validated DNS records, specifically SPF, DKIM, and DMARC.

These records help verify that outgoing mail originates from trusted servers and are now mandatory for high-volume senders.

Failures in authentication directly affect mail deliverability and increase the likelihood of messages being rejected or flagged as spam.

Analytics and performance reporting

Transactional email services offer analytics dashboards that include metrics such as:

• Open rates
• Click-through rates
• Bounce rates
• Spam complaint rates
• Delivery status logs

Advanced features also include monitoring inbox placement and real-time feedback loops to identify and isolate issues that affect deliverability. AI-driven insights are being increasingly applied to predict changes in deliverability trends and detect anomalies in email behavior.

Dedicated IP addresses

Organizations with high email throughput requirements often utilize dedicated IP addresses to ensure optimal performance. This enables them to build and maintain a consistent sender reputation independent of other users.

A consistent IP history improves acceptance rates and reduces reliance on shared IP pools, which may be affected by the behavior of different senders.

IP warm-up

IP warm-up is the process of gradually increasing the volume of mail sent from a new IP address. Transactional email providers automate this process to establish a positive reputation with recipient mail servers.

Without warm-up, new IPs risk being throttled or rejected due to unknown sender status.

AI-driven security and phishing detection

AI-generated phishing campaigns increasingly target transactional email systems. In response, providers have integrated AI-powered spam filtering to identify content patterns consistent with malicious activity.

These tools now play a role in defending against impersonation, fake login attempts, and malicious links embedded in transactional emails.

Regulatory compliance and privacy controls

Stricter global privacy regulations, such as the GDPR and similar laws in other jurisdictions, affect the handling of user data in transactional email systems. Providers must implement:

• Logging limitations.
• Consent tracking.
• Encryption for sensitive data.
• Clearly defined retention policies.

Transactional email services are now required to offer built-in controls to support compliance obligations, mainly when operating in regulated sectors such as finance or healthcare.

Further reading:

• Compare Email Marketing Pricing: Top 15 Providers in 2025
• Generative AI for Email Marketing: Applications & Examples

External Links

• 1. 15 Transactional Email Examples and why They Work - MailerSend .