Introduction – Targeting the right email service provider
Choosing the right email service provider means building the backbone of your clients’ messaging and digital identity.
With increasing concerns about security, compliance, automation, and domain branding, domain resellers, web hosting providers, and digital agencies must choose their email platform over more than just inbox space.
In fact, modern tools empower users with custom domain capabilities, white-label options, robust deliverability rates, enhanced spam protection, and scalable infrastructure.
This guide ranks and compares the 10 best email service providers based on features, reliability, and customer reviews around the web.
Table of content
What to look for in an email service provider
With hundreds of email service providers (ESPs) on the market, narrowing down the options requires a clear understanding of what drives performance, efficiency, and long-term value.
Here are the most important features and qualities to evaluate:
1. Custom domain support
Domain and web service resellers know that sending emails from a generic domain like @gmail.com doesn’t cut it: representing the digital identity of the brand and accessing advanced security features are the essentials to generate trustworthiness for a business.
2. Deliverability and spam filtering
It doesn’t matter how great your message is if it ends up in the spam folder.
The best ESPs maintain excellent sender reputations, enforce industry standards like SPF, DKIM, and DMARC, and offer robust filtering systems that ensure your emails reach inboxes.
3. Security and compliance
Whether you’re managing client data or handling sensitive internal communications, security is non-negotiable.
Look for providers offering S/MIME encryption and digital signatures, two-factor authentication (2FA), GDPR compliance, Single Sign-On (SSO), and advanced anti-phishing measures.
4. Ease of use and scalability
Usability matters.
A good email provider should offer a clean interface, easy setup, and admin features that scale with your business, such as role management, shared mailboxes, and user-level permissions.
5. Integration and automation capabilities
Tech-savvy businesses get how useful it is to integrate the existing tech stack with other tools, and provisioning systems like WHMCS.
6. White-label options for resellers
If you’re reselling services under your own brand, white-label email solutions are a must. They enable you to offer professional-grade email services while maintaining full control over your customer experience.
7. Reliable support and documentation
Whether it’s onboarding assistance or resolving a technical glitch, responsive support makes a big difference.
The top ESPs back their offerings with well-maintained documentation, user guides, and responsive support teams that understand the needs of hosting companies, agencies, and IT professionals.
In the next section, we’ll walk you through the top email service providers of 2025, covering their features and who they’re best suited for.
TL;DR – 10 top business email service providers
| Name | Mailbox size | Ideal for | Multiple domains | Email aliases |
| Openprovider Mail | Custom, starting from 15GB | Domain service resellers | ✅ Yes | ✅ 50+ aliases per mailbox (reseller-configurable) |
| Gmail (Google Workspace) | 30 GB – 5 TB (plan-dependent) | SMEs, remote teams, solo professionals | ✅ Yes | ✅ Up to 30 aliases per user |
| Outlook (Microsoft 365) | 50 GB – 1.5 TB (plan-dependent) | Enterprises, hybrid workplace teams | ✅ Yes | ✅ Up to 400 aliases per user |
| Proton Mail | 1 GB – 500 GB | Privacy-focused users & small teams | ✅ Yes (on paid plans) | ✅ 5–50 aliases (plan-dependent) |
| iCloud Mail | 5 GB – 12 TB (with iCloud+) | Apple users and solopreneurs | ❌ No | ✅ 3 aliases |
| Zoho Mail | 5 GB – 100 GB | SMBs and tech-forward agencies | ✅ Yes | ✅ Up to 30 aliases per user |
| Neo Mail | 10 GB – 100 GB | Solopreneurs, freelancers, startups | ✅ Yes (on paid plans) | ✅ 10–50 aliases (depending on plan) |
| Fastmail | 2 GB – 100 GB | Tech-savvy users, developers | ✅ Yes | ✅ Up to 600 aliases per account |
| Tutanota | 1 GB – 100 GB | Encrypted communication advocates | ✅ Yes (on paid plans) | ✅ 5–20 aliases (plan-dependent) |
| Mailfence | 500 MB – 50 GB | Compliance-focused professionals | ✅ Yes | ✅ 10 aliases on premium plans |
This guide was developed through in-depth market research and hands-on insights from Openprovider’s team of domain infrastructure experts, who support thousands of resellers, hosting providers, and digital agencies worldwide.
It aims to deliver a balanced and practical overview of the best email service providers of 2025, considering real-world needs such as scalability, white-label capabilities, and multi-domain management. Our goal is to help decision-makers in the domain services ecosystem make informed, business-driven choices, while recognizing the value each provider brings to the evolving email landscape.
A deep dive into the features of email service providers
Ideal for domain resellersMailbox storage: 15 GB per mailbox (+ 5GB expansion packs).
Openprovider business email solution is tailored for domain service resellers, offering scalable solutions with robust security features.
Features
- Unlimited aliases per mailbox
- Fully white labeled
- Support for multiple domains
- Advanced spam filtering
- No cap on number of inboxes
- Primarily designed for resellers
Best for Google workspace usersMailbox storage: 15 GB, with up to 5 TB with paid plans
Gmail is one of Google’s most popular products. It offers a user-friendly interface with robust integration into Google’s ecosystem, making it ideal for businesses already using Google services.
Pros:
- Strong spam protection
- Seamless integration with Google apps
- Reliable uptime
Cons:
- Privacy concerns due to data scanning
- Limited customization for advanced users
Best for Microsoft users
Mailbox storage: 100 GB – 1.5 TB (plan-dependent)
Outlook integrates deeply with Microsoft Office tools, offering a familiar environment for businesses reliant on Microsoft products.
Pros:
- Fluid collaboration across MIcrosoft’s apps
- Robust calendar and task management
- Advanced security features
- High attachment size limit
Cons:
- Can be resource-intensive and less scalable for medium-big businesses
- Complex setup for non-Windows users
The privacy-focused provider
Mailbox Storage: 1 GB – 50 GB (plan-dependent)
Proton Mail emphasizes security with end-to-end encryption, catering to users who prioritize privacy.
Pros:
- End-to-end encryption
- No personal information required for signup
- Open-source codebase
Cons:
- The user-based pricing for businesses may limit scalability
- Integrations might be more limited, and connectivity with other email clients is dependant on a secondary product (Proton Bridge)
Best for Apple users
Mailbox Storage: 5 GB – 12 TB (with iCloud+)
iCloud Mail is optimized for Apple devices, providing seamless synchronization across the Apple ecosystem.
Pros:
- Smooth integration with Apple devices
- User-friendly interface
- Generous and expandable storage
Cons:
- Not focused on businesses and resellers
- Limited customization and volume-capped messages
- Not ideal for non-Apple users
Feature-rich for businesses
Mailbox Storage: 5 GB, 10 GB or 50 GB (plan-dependent)
Zoho Mail offers a comprehensive suite of tools tailored for businesses, including CRM integration and collaboration features.
Pros:
- Ad-free experience
- Integrated with Zoho’s suite of apps
- RevOps-focused, with strong administrative controls
Cons:
- Learning curve for new users
- Not reseller-focused
- Full potential reached better when connected to other Zoho’s tools
Ideal for small teams
Mailbox Storage: 15 GB (only 5 are cloud) to 100 GB (plan-dependent)
Neo Mail focuses on simplicity and efficiency, making it suitable for startups and small teams seeking straightforward email solutions.
Pros:
- Clean and intuitive interface
- Affordable pricing
- Custom domain support
Cons:
- Limited advanced features
- Smaller user community
Speed and simplicity
Mailbox Storage: 5 GB – 100 GB
Fastmail offers a fast, no-frills email experience with a focus on user privacy and minimalism.
Pros:
- Offers a free trial
- Market-aligned pricing
Cons:
- Limited integrations
- Reports on missing end-to-end and PGP encryption
- Smaller user community
Secure and open-source
Mailbox Storage: 50 GB – 1 T
Tutanota provides encrypted email services with a commitment to open-source development and user privacy.
Pros:
- End-to-end encryption
- Offers autoresponders and secure web embeddings
Cons:
- Limited third-party integrations
- Limited-to-no IMAP/POP support
Privacy with productivity
Mailbox Storage: 40 GB – 225 GB
Mailfence combines secure email with productivity tools like calendars and document storage, targeting privacy-conscious professionals.
Pros:
- Digital signatures support
- Integrated suite of tools
- No ads
Cons:
- Limited storage on free plan
- Recipient-based limitations
- Interface can feel dated
How Openprovider supports resellers and agencies
From capped daily email sends, low mailbox storage, to subpar spam protection, managing professional email services across multiple clients means dealing with limits that undermine service reliability and customer satisfaction.
Openprovider addresses these challenges head-on for domain resellers and agencies with an email solution offering generous 15 GB mailboxes (expandable), unlimited aliases, and high-volume message capabilities tailored for B2B usage.
With strong anti-spam filters, white-labeled mailboxes provision and the chance to buy domains directly at cost-price, we provide a secure, scalable, and centralized way to manage email alongside domain portfolios, ideal for domain reseller businesses who demand efficiency, uptime, and client trust.
Conclusions – Select your email service provider
Choosing the right email service provider in 2025 is about finding a solution that matches your business model, security needs, and growth plan, rather than mere mailbox size or user interface.
Openprovider offers tailored capabilities that give resellers and agencies a clear edge to keep offering to their clients manageable and scalable digital services.
Learn more on why resellers across the globe have already chosen our business email solutions.
