Email Server
What is an email server?
Quick answer: an email server is the system that sends, receives, stores and routes electronic messages. SMTP handles sending. IMAP or POP3 let you access the messages you receive. For businesses, the choice affects security, deliverability and the ability to grow.
Every time you click “Send”, a chain of processes kicks off that usually stays invisible. Within seconds, your message passes through different systems until it reaches the right mailbox.
The email server sits at the center of that journey. Understanding what it does helps you set up accounts, fix problems and choose better tools for your business.
It also helps you tell apart corporate email, transactional emails and email marketing campaigns. Although they all use sending infrastructure, they meet different needs.
What is an email server?
An email server is a computer or program that handles messages over a network. It can send, receive, forward, filter and store emails.
Think of it as a digital post office. The system identifies the destination, checks the route and delivers each message to the right service.
The term covers several functions. Some process outgoing mail. Others receive messages and keep them until you open your inbox.
In a company, this system also manages domains, users, permissions, queues and security policies. It also logs errors that help diagnose problems.
Basic components of an email server
Several pieces are involved behind a simple action:
- Email client or MUA: the application where you write and read emails, such as Outlook, Thunderbird or a webmail.
- Submission agent or MSA: accepts the message from the authenticated user and prepares it for transfer.
- Transfer agent or MTA: routes the email between servers using SMTP.
- Delivery agent or MDA: places the message in the recipient’s mailbox.
- DNS: publishes the records that indicate where to receive email and who can send it.
You don’t need to memorize these acronyms. However, understanding how the tasks are divided makes any later setup easier.
How does an email server work, step by step?
An email’s journey can be summed up in seven stages:
- You write the message in your email client and click “Send”.
- The application connects to the outgoing mail server using SMTP.
- The system authenticates your account and checks the message data.
- The server queries DNS to find the MX records of the receiving domain.
- The message travels to the recipient’s email server.
- The receiving system applies reputation, authentication and content checks.
- The email becomes available in the inbox through IMAP, POP3 or webmail.
If the destination doesn’t respond, the message may stay in a queue. The server will keep retrying for a limited period.
When delivery is impossible, it usually generates a bounce. That notice includes a code that explains the reason for the rejection.
Types of email servers: SMTP, IMAP and POP3
SMTP, IMAP and POP3 usually appear together in any settings panel. However, they don’t do the same job.
| Protocol | Main function | Typical use | Key advantage |
|---|---|---|---|
| SMTP | Sending and transferring emails | Outgoing mail | Connects servers and applications |
| IMAP | Accessing and syncing emails | Incoming mail | Keeps multiple devices in sync |
| POP3 | Downloading emails | Incoming mail | Makes local and offline access easy |
SMTP server for outgoing mail
SMTP stands for Simple Mail Transfer Protocol. It is the standard protocol used by an outgoing mail server.
Its job is to accept the message, identify the receiving domain and transfer it. It can also relay it to another intermediate system.
A specialized SMTP service adds capacity, tracking and error handling. It is useful for applications, online stores, CRMs and high-volume sending.
IMAP server to sync incoming mail
IMAP keeps messages on the server. Your computer and your phone show the same status, the same folders and the same changes.
If you mark an email as read on one device, it will appear as read on the others. That is why it is usually the most convenient option for teams and users with multiple devices.
POP3 server to download messages
POP3 downloads email to the device. Depending on the settings, it can then delete the copy stored on the email server.
This protocol uses less remote storage. However, it makes syncing across several devices harder and requires you to take care of local backups.
Difference between an email server, client, webmail and provider
These concepts are often confused because the same company can offer them together.
| Concept | What it does | Example of use |
|---|---|---|
| Email server | Processes and transports messages | Sends via SMTP and receives for IMAP |
| Email client | Lets you write, read and organize emails | An installed application |
| Webmail | Provides a client in the browser | Checking your mailbox on a website |
| Email provider | Provides the infrastructure and the service | Hosting accounts with your own domain |
| Email marketing platform | Manages contacts, campaigns and metrics | Sending newsletters with consent |
Your client is the interface you see. The email server does the technical work behind that interface.
Webmail is also a client. The difference is that it runs in the browser and doesn’t require an installed application.
How do I find out what my email server is?
You can find it in your provider’s dashboard, in your account settings or in its documentation. Look for fields such as “incoming server”, “IMAP”, “POP” or “SMTP”.
The name usually follows formats such as imap.tudominio.com, smtp.tudominio.com or mail.tudominio.com. It’s best not to guess it, because each provider defines its own values.
You’ll need several details to set up an account:
- Server name or address.
- Connection port.
- Encryption type.
- Username, usually the full email address.
- Password or authentication method.
- Authentication requirement for outgoing mail.
If you manage the domain, you can also check its MX records. They indicate which email server accepts incoming messages.
Email server ports and secure connections
A port identifies the channel used by each service. The most common values are the following:
| Service | Common port | Protection or use |
|---|---|---|
| SMTP | 587 | Authenticated sending with STARTTLS |
| SMTP | 465 | Sending with implicit TLS |
| SMTP | 25 | Transfer between servers |
| IMAP | 993 | Secure access via TLS |
| POP3 | 995 | Secure download via TLS |
Always use the combination specified by your provider. A correct port with the wrong encryption can also prevent the connection.
Port 25 is usually reserved for communication between servers. To send from an application or client, providers usually offer 587 or 465.
Email server security: SPF, DKIM, DMARC and TLS
Security doesn’t depend on a single tool. A reliable environment combines encryption, authentication, filters, access control and monitoring.
SPF is a DNS record. It indicates which systems can send messages on behalf of your domain.
The receiving server checks that list. If the source isn’t authorized, the risk of rejection or being classified as spam increases.
DKIM signs each message
DKIM adds a cryptographic signature to the email header. The recipient validates it using a public key published in DNS.
This check helps confirm the origin. It also detects changes made in transit.
DMARC defines a protection policy
DMARC uses the results of SPF and DKIM. It also lets you specify how to handle messages that fail the checks.
Its reports help detect spoofing and forgotten sending sources. It’s best to apply it gradually to avoid blocking legitimate email.
TLS protects transport
TLS encrypts the connection between compatible systems. This reduces the exposure of content and credentials in transit.
You also need strong passwords, multi-factor authentication and backups. You should also keep any software managed by your company up to date.
Your own email server or a managed service: which is better?
Your own server gives you control over data, rules and infrastructure. In return, it requires technical knowledge and constant monitoring.
You’ll have to manage updates, IP reputation, queues, DNS records and filtering. You’ll also have to deal with outages, abuse and blocklists.
A managed service reduces that burden. The provider maintains the infrastructure and offers dashboards, support, scalability and security mechanisms.
Before choosing, consider these questions:
- How many accounts and messages do you need to manage?
- Can your team maintain the service every day?
- Do you need to keep data in a specific location?
- What availability and disaster recovery does the business require?
- Will you send conversations, notifications or bulk campaigns?
- Will you have support when a delivery problem appears?
For many SMBs, a managed provider is more practical. Organizations with specific requirements may prefer their own or a hybrid environment.
Corporate email, transactional email and email marketing
A company may need three different flows. Keeping them separate improves organization and protects the reputation of each type of sending.
Corporate email between people
It includes everyday conversations from addresses such as [email protected]. It needs mailboxes, incoming mail, a calendar and access from different devices.
Transactional emails from an application
These are purchase confirmations, shipping notices, invoices or password resets. Users expect them after taking an action.
These messages require speed and tracking. You can send them using a professional SMTP server or API.
Email marketing campaigns
Newsletters and promotions are sent to subscriber lists with consent. They need segmentation, automatic unsubscribes, templates, testing and statistics.
Using a corporate mailbox for large campaigns creates limitations. It also makes it harder to manage bounces, unsubscribes and complaints.
How does Mailrelay relate to an email server?
At Mailrelay we help you with the sending layer for campaigns and transactional messages. Your usual provider can keep hosting your corporate email and inboxes.
With us you can create newsletters, manage subscribers and build simple automations. You can also connect your software via SMTP or API.
Our infrastructure is designed for sending email marketing. It includes our own IP ranges and tools to improve the deliverability of your campaigns.
We also handle bounces, unsubscribes and spam complaints. Reports show opens, clicks and delivery issues in real time.
You can send transactional emails from a website, a CRM or an application. That way you benefit from infrastructure built for that job.
Our free plan lets you send up to 80,000 emails a month to 20,000 contacts. We also offer expert, multilingual support on all accounts, including the free one.
If you have a technical question, you can contact us by phone, chat or ticket. This support is especially useful when authenticating a domain or reviewing an error.
How to set up an email server without errors
Each provider has its own instructions, but this sequence works as a checklist:
- Confirm whether you need SMTP, IMAP, POP3 or an API.
- Copy the server name from the official dashboard.
- Enter the recommended port and enable TLS.
- Add the username and password without extra spaces.
- Enable authentication for the outgoing server.
- Set up SPF and DKIM in the domain’s DNS.
- Define a gradual DMARC policy and review its reports.
- Send a test to several email providers.
- Check headers, bounces and the spam folder.
- Document the changes for future incidents.
Never share credentials in public documents. In applications, use a secrets manager or the secure system available.
Common email server problems and how to fix them
I can receive emails but can’t send them
Check the SMTP server, the port and outgoing authentication. Also check the password and any firewall restrictions.
I can send emails but can’t receive them
Check the available storage, the MX records and the IMAP or POP3 settings. Also review filters and forwarding rules.
Messages go to spam
Check SPF, DKIM and DMARC. Then analyze the domain’s reputation, the quality of the list and the content sent.
Keep a steady volume. Also remove invalid addresses and honor unsubscribes right away.
The server rejects the password
Make sure you use the full email address as the username. If you have two-step verification, you may need OAuth or an app password.
A certificate error appears
Check the server name and the date of the TLS certificate. Avoid accepting unknown certificates just to move on quickly.
The email is stuck in the queue
The destination may be temporarily unreachable. Check the response code before resending manually.
How to choose an email server for your business
The best option is the one that fits your actual use. Price matters, but it should be weighed together with security and reliability.
Check these criteria:
- Infrastructure availability and redundancy.
- Sending and storage capacity.
- Compatibility with SMTP, IMAP, API and your applications.
- Authentication with SPF, DKIM and DMARC.
- Handling of bounces, complaints and unsubscribes.
- Logs and reports that are easy to interpret.
- Scaling without complex changes.
- Accessible technical support that solves problems.
- Privacy and access controls.
- Total cost of administration.
If your goal is to send campaigns, choose an email marketing platform built for that volume. For internal conversations, prioritize mailboxes, collaboration and archiving.
When you need both, combine specialized services. That separation makes diagnosis easier and reduces the impact of an incident.
A good email server also protects your results
Email depends on many coordinated pieces. SMTP handles outgoing mail, IMAP or POP3 provide access and DNS points to the right route.
Technical setup affects delivery. However, reputation, consent and contact quality also count.
At Mailrelay we bring together sending, automation and analytics tools in one simple dashboard. Plus, our team can help you even if you use the free account.
Frequently asked questions about email servers
What is an email server in simple terms?
It’s the system that transports and stores emails. It receives your message, finds the destination and delivers it to the corresponding server.
What is my account’s email server?
It depends on your provider. Check the settings panel or its documentation and look for the SMTP, IMAP or POP3 details.
Is SMTP the same as an email server?
SMTP is a protocol for sending emails. An email server can use SMTP and also include receiving, storage, filters and other functions.
What is the difference between IMAP and POP3?
IMAP syncs the messages stored on the server across several devices. POP3 usually downloads them to store them locally.
Which incoming mail server should I use?
IMAP is usually more practical if you check your email from several devices. POP3 can be useful for keeping a local copy on a single computer.
What ports does a secure email server use?
The most common are 587 or 465 for SMTP, 993 for IMAP and 995 for POP3. Always follow your provider’s values.
Can I create my own email server?
Yes, but you’ll have to maintain software, security, DNS, reputation, backups and availability. A managed service reduces that operational work.
Why does an email leave the server but end up in spam?
Technical delivery doesn’t guarantee reaching the inbox. Filters also evaluate authentication, reputation, content, complaints and sending behavior.
Does Mailrelay replace my corporate email?
Your provider can keep managing mailboxes and incoming messages. At Mailrelay we provide infrastructure for campaigns, automations and transactional emails via SMTP or API.
Can I use Mailrelay as an SMTP server?
Yes. You can connect applications, CRMs or compatible clients to Mailrelay’s SMTP. You’ll also get reports and automatic handling of delivery issues.