An email server is a software system (and the hardware hosting it) that manages the sending, receiving, and storage of email messages. Every time you send an email, at least two mail servers are involved: yours and the recipient's.
Without this component, email as we know it simply would not exist.
What Does an Email Server Actually Do?
An email server performs three main functions:
- Send messages: it takes the email you compose and routes it to the recipient's server over the internet.
- Receive messages: it accepts incoming emails from other servers and deposits them in the correct mailbox.
- Store messages: it keeps emails in folders (Inbox, Sent, Spam, etc.) until the user reads or deletes them.
To accomplish these tasks, mail servers rely on several specialized protocols, explained below.
The Protocols That Move Email: SMTP, IMAP, and POP3
There is no single email protocol — each stage of the process uses a different one.
SMTP — Simple Mail Transfer Protocol
SMTP is the sending protocol. When you click "Send," your email client (Outlook, Gmail, Thunderbird) connects to your outgoing SMTP server and hands it the message. The sender's SMTP server then contacts the recipient's SMTP server to deliver it.
- Standard port: 25 (server to server), 587 (client to server, recommended).
- With TLS/SSL encryption: port 465.
IMAP — Internet Message Access Protocol
IMAP is the synchronized access protocol. Messages stay on the server; your client displays them without permanently downloading them. This lets you read the same email on your phone, tablet, and computer, always in sync.
- Standard port: 143 (with STARTTLS), 993 (SSL/TLS).
POP3 — Post Office Protocol version 3
POP3 is the local download protocol. It downloads messages to your device and (by default) deletes them from the server. It is useful if you access email from only one device and want to save server storage, but it does not sync across multiple devices.
- Standard port: 110, or 995 with SSL/TLS.
| Protocol | Function | Messages on server | Multi-device |
|---|---|---|---|
| SMTP | Sending | N/A | N/A |
| IMAP | Access / reading | Yes (they stay) | Yes |
| POP3 | Download | No (they are deleted) | No |
How Does an Email Travel From Start to Finish?
The journey of a message seems instant, but it involves several steps:
- Composing and sending: you write the message in your email client and click "Send."
- Outgoing SMTP connection: your client authenticates with your SMTP server and hands it the message.
- DNS lookup (MX record): your SMTP server queries DNS for the MX record of the recipient's domain to find out which server to deliver the email to.
- Delivery to destination server: your SMTP server connects to the recipient's SMTP server and transfers the message.
- Mailbox storage: the destination server stores the email in the recipient's mailbox.
- Download or access: the recipient opens their email client and retrieves the message via IMAP or POP3.
This entire process usually completes in seconds, though it can take longer if there are network issues or if the message is held in an anti-spam queue.
Types of Email Servers: Hosted vs. Self-Hosted
There are two main options for managing email for a domain:
Hosted Email (Cloud-Based)
A third party manages the server for you. Examples: Google Workspace, Microsoft 365, Zoho Mail. Advantages: no technical maintenance, high availability, polished interface. Disadvantage: monthly cost per mailbox and less control over your data.
Self-Hosted Mail Server
You install and manage the mail server software yourself on a server or VPS. Software examples: Postfix + Dovecot, Exim, Zimbra, Mail-in-a-Box. Advantages: full control, no per-user mailbox limits, fixed costs. Disadvantage: requires technical setup and ongoing maintenance (updates, blacklist monitoring, IP reputation management).
If you are interested in setting up your own mail server on a VPS, browse our VPS server guides for step-by-step walkthroughs.
For businesses that prefer to skip the technical complexity, elenlace.com provides full corporate email setup and migration services.
Email Server Security: What You Cannot Ignore
A poorly configured mail server is an open door to spam, phishing, and credential theft. These are the essential security mechanisms:
- SPF (Sender Policy Framework): a DNS record that specifies which servers are authorized to send email from your domain.
- DKIM (DomainKeys Identified Mail): a cryptographic signature that guarantees the message was not altered in transit.
- DMARC: a policy that combines SPF and DKIM and tells receiving servers what to do if a message fails verification (reject, quarantine, or take no action).
- TLS: encrypts the connection between servers to protect the message during transport.
- Anti-spam filter: analyzes message content and sender reputation to classify messages as legitimate or spam.
Without SPF, DKIM, and DMARC properly configured, your emails will very likely end up in recipients' spam folders.
Key Takeaways
- An email server handles sending (SMTP), access (IMAP), and downloading (POP3) of messages.
- IMAP keeps messages synced on the server; POP3 downloads them to the device. For multi-device use, IMAP is the right choice.
- An email's journey involves DNS lookups (MX records), SMTP authentication, and mailbox storage.
- You can use cloud-hosted email or run your own server on a VPS depending on your needs.
- SPF, DKIM, and DMARC are mandatory for good deliverability and to avoid spam classification.
Need to set up or migrate your company's corporate email? The team at elenlace.com handles the full technical configuration so you can focus on writing your messages.
FAQ
What is the difference between IMAP and POP3?
IMAP keeps messages on the server and syncs them across all your devices. POP3 downloads them to the device and deletes them from the server by default. If you use email on more than one device, always choose IMAP.
Why are my emails going to spam?
The most common causes are: missing SPF, DKIM, or DMARC records; a server IP with a poor reputation (blacklisted); content that triggers spam filters; or a new domain with no sending history. Fixing your DNS configuration and using a clean IP address usually resolves the issue.
Do I need my own mail server, or is Gmail/Outlook enough?
For most small and medium businesses, a hosted service like Google Workspace or Microsoft 365 is sufficient and much easier to maintain. A self-hosted server makes sense if you have strict privacy requirements, a large number of mailboxes, or want full control over your data and long-term costs.
What is an MX record?
An MX (Mail Exchanger) record is a DNS entry for your domain that tells other mail servers where to deliver messages addressed to that domain. Without a correctly configured MX record, no one can send you email at your custom domain address.
Further reading
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