What are Incoming and Outgoing Mail Server 2026? Best Guide

Incoming and outgoing mail servers are the two systems your email app uses to receive and send messages.

The incoming mail server (IMAP or POP3) downloads or syncs mail to your device, while the outgoing mail server (SMTP) delivers your messages to recipients. Correct servers, ports, and encryption settings ensure reliable, secure email.

Email only works when your app knows where to fetch new messages and where to send them. Here, we’ll demystify the incoming and outgoing mail server settings, explain IMAP vs POP3 and SMTP, share the right ports and encryption, and walk you through setup, testing, and troubleshooting—based on real-world hosting experience.

What Are Incoming and Outgoing Mail Servers?

Every email account uses two servers:

Incoming mail server: Retrieves mail to your device via IMAP or POP3.
Outgoing mail server: Sends mail from your device to recipients via SMTP.

Most hosting providers use hostnames like mail.yourdomain.com, imap.yourdomain.com, or smtp.yourdomain.com. Your username is usually your full email address, and you should use SSL/TLS encryption with authentication enabled.

Incoming Mail Server: IMAP vs POP3

Your incoming mail server handles downloads and synchronization. You’ll choose between IMAP or POP3 during setup.

IMAP (Recommended for Most Users)

Syncs email across all devices (server is the “source of truth”).
Folders, read/unread state, and sent items are consistent everywhere.
Best for phones, laptops, and webmail used together.

POP3 (Legacy/Offline Use Cases)

Downloads and can remove messages from the server (local storage).
Good for simple, single-device workflows or limited server storage.
Risks losing a centralized archive if not configured to leave copies on the server.

Outgoing Mail Server: SMTP Explained

SMTP (Simple Mail Transfer Protocol) is used to deliver your messages to your recipient’s mail server. Your outgoing server must require authentication and use encryption to prevent abuse and protect credentials.

SMTP Authentication: Always enable “My outgoing server (SMTP) requires authentication.”
Encryption: Use SSL/TLS or STARTTLS to secure the connection.
Ports: Prefer 587 (STARTTLS) or 465 (Implicit TLS). Avoid port 25 on clients.

Recommended Ports and Encryption (Quick Reference)

IMAP Secure: 993 (SSL/TLS)
IMAP Non-Encrypted/STARTTLS: 143 (STARTTLS recommended if available)
POP3 Secure: 995 (SSL/TLS)
POP3 Non-Encrypted/STARTTLS: 110 (STARTTLS recommended if available)
SMTP Secure: 465 (SSL/TLS) or 587 (STARTTLS)
SMTP Legacy: 25 (often blocked; don’t use on clients)

Tip: If your provider supports both 587 (STARTTLS) and 465 (SSL/TLS), choose the one they recommend. Many modern hosts default to 587 with STARTTLS for better compatibility.

How to Find Your Mail Server Settings?

Check your hosting dashboard or cPanel/Plesk for Email Accounts > Configure Mail Client.
Look for server names, ports, and encryption type (SSL/TLS or STARTTLS).
Username is typically the full email address; password is your mailbox password (or an app password if using 2FA).
If you host DNS with your provider, verify MX records point to the correct mail host.

Step-by-Step Setup in Popular Email Clients

Information to Gather First

Incoming server: imap.yourdomain.com or mail.yourdomain.com (IMAP 993 SSL/TLS)
Outgoing server: smtp.yourdomain.com or mail.yourdomain.com (SMTP 587 STARTTLS or 465 SSL/TLS)
Username: full email address
Password: mailbox password
Authentication: required for SMTP

Apple Mail (macOS/iOS)

Add Account > Other Mail Account.
Enter name, email, and password.
Incoming: IMAP, host, username, password, SSL on, port 993.
Outgoing: host, username, password, SSL on, port 587 or 465, auth enabled.

Microsoft Outlook (Windows/Mac)

File > Add Account > Advanced setup > IMAP.
Incoming: server, port 993, encryption SSL/TLS.
Outgoing: server, port 587 (STARTTLS) or 465 (SSL/TLS), auth required.
Check “My outgoing server (SMTP) requires authentication.”

Thunderbird

Account Settings > Account Actions > Add Mail Account.
Let it auto-detect, then verify ports and encryption.
Ensure SMTP uses authentication and TLS.

Testing and Verifying Your Mail Servers

Use these commands to confirm connectivity, certificates, and STARTTLS support:

# Test IMAP over TLS
openssl s_client -connect imap.example.com:993 -crlf -quiet

# Test SMTP with STARTTLS (recommended on 587)
openssl s_client -starttls smtp -connect smtp.example.com:587 -crlf -quiet

# Check MX records for your domain
dig +short MX yourdomain.com

# Basic SMTP banner check (if allowed)
telnet smtp.example.com 587

If the certificate’s Common Name (CN) or SAN doesn’t match your server hostname, update your mail client to use the correct host (often the one shown in your hosting control panel) or ask your host to align SSL.

Common Problems and How to Fix Them

“Can Receive but Can’t Send”

Switch SMTP port to 587 (STARTTLS) or 465 (SSL/TLS); avoid 25.
Enable SMTP authentication (use full email address and password).
Confirm the correct outgoing server hostname and encryption type.
Check ISP or network firewalls blocking ports 465/587.

SSL/TLS Certificate Errors

Use the exact hostname your certificate secures (e.g., mail.yourdomain.com).
Renew or reissue expired/mismatched certificates (AutoSSL helps).
Avoid using raw IPs; they rarely match certs.

Login Failures

Confirm the mailbox password (try webmail to verify).
Use the full email address as the username.
If using 2FA, generate and use an app password.
Check for account lockouts or rate limits after multiple failed attempts.

Mail Delays or Rejections

Ensure SPF, DKIM, and DMARC are correctly configured.
Check your IP/domain reputation and avoid sending bulk mail from shared SMTP.
Verify recipient address, mailbox quota, and that your message isn’t flagged as spam.

Email Security Essentials: SPF, DKIM, DMARC

Deliverability and trust depend on proper DNS authentication. Set these records for your domain:

SPF: Authorizes which servers can send mail for your domain.
DKIM: Cryptographically signs your messages to prevent tampering.
DMARC: Tells recipients how to handle failed SPF/DKIM and provides reporting.

Together, they reduce spoofing, improve inbox placement, and protect your brand. Many hosts, including QloudHost, provide one-click DKIM and guided SPF/DMARC setup.

Real-World Choices: When to Use IMAP vs POP3

Teams and multi-device users: IMAP keeps everything synced.
Travelers with intermittent internet: IMAP plus offline caching in your client.
Single desktop with backup routines: POP3 can work if you leave copies on the server and back up locally.
Limited server storage: POP3 may help, but ensure you archive safely.

Best Practices for Reliable, Secure Email

Prefer IMAP (993) and SMTP (587/465) with SSL/TLS.
Enable SMTP authentication and avoid port 25 in clients.
Use strong passwords or app passwords and enable 2FA where possible.
Set up SPF, DKIM, and DMARC.
Keep DNS, MX, and mail records consistent after migrations.
Monitor mailbox quotas and storage usage.
Test with openssl s_client when diagnosing issues.

How QloudHost Helps?

On QloudHost hosting, secure IMAP/SMTP is enabled by default, AutoSSL keeps certificates fresh, and DKIM is one click.

Our cPanel “Configure Mail Client” page shows exact incoming and outgoing mail server settings, and 24/7 support can help you fix send/receive errors, SPF/DMARC alignment, and client configuration fast.

FAQs: Incoming and Outgoing Mail Server

What should I use for my incoming and outgoing mail server names?

Use the hostnames provided by your host, commonly mail.yourdomain.com for both. Some providers separate by protocol (imap.yourdomain.com and smtp.yourdomain.com). Always match the hostname to the SSL certificate shown in your control panel to avoid certificate warnings.

Should I choose IMAP or POP3 for incoming mail?

Choose IMAP if you use multiple devices or want server-side folders and consistent sync. Choose POP3 only for single-device setups with local archiving and limited server storage. If using POP3, consider “leave a copy on server” to prevent data loss.

What’s the best SMTP port: 587, 465, or 25?

Use 587 with STARTTLS or 465 with SSL/TLS. Avoid 25 for clients—many ISPs block it and it’s intended for server-to-server mail. Ensure “SMTP authentication” is enabled and encryption is set to STARTTLS (587) or SSL/TLS (465).

Why can I receive emails but not send them?

Common causes include using port 25, disabled SMTP authentication, wrong outgoing server/hostname, or blocked ports by your network. Switch to 587 (STARTTLS) or 465 (SSL/TLS), enable authentication, confirm credentials, and check firewall/ISP restrictions.

How do I find my mail server settings in cPanel or Plesk?

In cPanel, go to Email Accounts > Connect Devices (or Configure Mail Client) to see incoming/outgoing servers, ports, and encryption. In Plesk, open Mail > your mailbox > Mail Settings. If unsure, contact your host’s support for the exact details.