Good day. A multinational corporation with branches in various nations intends to implement its email server.

We initially considered using Exchange, but it was ruled out due to the high implementation costs and the requirement for an Exchange specialist.

Another option we considered was Kerio or MDaemon, but they were discarded due to the perpetual subscription fees, which would eventually exceed the cost of Exchange over a five-year period.

We also thought about Exim or Postfix, but the added complexities and the difficulty in finding a full-time postmaster in our region made it an impractical choice.

That leaves us with a few remaining options to consider. Zimbra is one possibility, although we still have concerns regarding its backup capabilities and how well it handles spam.

We require an email solution for over 100 users that includes backup functionality, allows for management by an administrator with average technical expertise, and provides the ability to view employee correspondence in a centralized folder.

Additionally, we have four domains hosted in different countries on platforms such as Gmail, Yahoo. We aim to consolidate all these domains into a single hosting server to simplify management for a single IT administrator and ensure unified backups.

Here are a few potential solutions:

1. Postfix with Dovecot and virtual domains.
2. Zimbra (although it comes at a higher cost, it is a reliable option).

3. ISPmanager 6 or iRedMail.

Based on your requirements, here is an analysis of the remaining options:

1. Postfix with Dovecot and virtual domains: This option provides flexibility and reliability. Postfix is a widely used mail transfer agent (MTA) known for its stability, while Dovecot is a popular choice for the mail delivery agent (MDA) and IMAP/POP3 server. Using virtual domains allows you to manage multiple domains from a single server. However, it requires more technical expertise to set up and maintain compared to other options.

2. Zimbra: Zimbra is a comprehensive email solution that offers features like backup capabilities, spam handling, and centralized management. It is known for its user-friendly interface and robust collaboration features. While it could be a reliable choice, as you mentioned, there might be some concerns regarding backup capabilities and spam handling. It's recommended to thoroughly evaluate these aspects before finalizing Zimbra.

3. ISPmanager 6 or iRedMail: ISPmanager 6 is a web hosting control panel that includes email management capabilities. It offers features like domain management, email accounts, and backup functionality. iRedMail is another open-source mail server solution that provides a complete email solution with anti-spam and anti-virus features. Both options are relatively simpler to set up and manage compared to the previous options. However, they may not offer the same level of collaboration features as Zimbra.

4. Microsoft Office 365: Office 365 is a cloud-based solution provided by Microsoft that offers a range of email and collaboration features. It allows you to consolidate domains, manage email accounts, and provides backup functionality. This option eliminates the need for on-premises infrastructure and offers scalability for multinational corporations. However, it does come with subscription costs.

5. Google Workspace (formerly G Suite): Similar to Office 365, Google Workspace provides cloud-based email and collaboration services. It offers features like Gmail, Google Drive, and Google Docs, which can enhance productivity and collaboration among your employees. You can consolidate multiple domains and manage email accounts from a centralized platform. Again, this option involves subscription costs.

6. Zoho Mail: Zoho Mail is another cloud-based email solution that caters to both individual and business needs. It offers features like domain hosting, email account management, backup functionality, and spam protection. Zoho Mail provides a user-friendly interface and has competitive pricing options based on the number of users.

7. ProtonMail: If security and privacy are top priorities, consider ProtonMail. It is an encrypted email service that ensures end-to-end encryption of your communication. ProtonMail offers features like domain hosting, user management, and secure email access. However, it may not have the same level of collaboration features as other options.

In summary, Postfix with Dovecot and virtual domains can provide a reliable and flexible solution, but it requires more technical expertise. Zimbra offers a comprehensive email solution, but ensure to address concerns regarding backup and spam handling. ISPmanager 6 or iRedMail are simpler options, although they may not offer the same level of collaboration features. Ultimately, the choice depends on the specific needs and priorities of your multinational corporation.

The Zimbra + Proxmox Mail Gateway has proven to be a more convenient and practical option for antispam measures. The built-in solution was not to my liking. However, the backup process depends on the specific type of installation, desires, and capabilities. With over 300 accounts, most operations are done through the browser. This system has been running smoothly for over 6 years, operating around the clock.

However, I must note that the installation, configuration, and updating can be quite capricious. In my opinion, it is better to configure the system and then only make adjustments such as adding, deleting, or editing users. Alternatively, I highly recommend performing a full backup before making any changes to the configurations, as there is a risk of something going wrong.

Zimbra is just a collector from the same SMTP server, with an IMAP server and its own control interface. The necessary functions are not provided by Zimbra itself, but rather by the corresponding components, which depend on the organization's network setup.

Backup is typically done at the virtual machine level, although there is nothing preventing individual user mailbox backups as well.

As for management, what exactly do you mean? Adding or removing accounts? Viewing correspondence? Having all 100+ employee emails in one folder is not practical. However, it is possible to access a user's mailbox with their password or copy the mailbox to another location for viewing. These methods are workarounds, though, and an SMP (Simple Mail Transfer Protocol) mail server should be used for a proper solution. Unusual functionality should not be expected from an SMP mail server, as it is designed for basic email transfer.

Zimbra's a solid all-in-one, with decent spam filtering and backup options, but the licensing can bleed your budget and the learning curve isn't trivial for average admins.
ISPmanager 6 or iRedMail streamline deployment and management, bundling spamassassin, antivirus, and backup tools into a neat stack, making it friendlier for mid-level admins. However, beware vendor lock-in or limited scalability.