- Every email setup screen asks about SMTP, IMAP and POP3, and most people guess.
- This plain-language guide explains what each protocol does, which ports matter, and which choice fits your team.
Every time you add an email account to a phone or Outlook, three acronyms appear: SMTP, IMAP and POP3. Most people click through on defaults and hope. Understanding them takes five minutes and saves hours of troubleshooting later — here is the plain-language version.
SMTP: The Sending Protocol
SMTP (Simple Mail Transfer Protocol) handles everything outgoing. When you press Send, your device hands the message to the SMTP server of your provider, which relays it to the recipient server. If SMTP settings are wrong you can usually still receive mail — you just cannot send, which is the classic half-broken setup.
IMAP: Reading Mail That Lives on the Server
IMAP (Internet Message Access Protocol) keeps all mail on the server and synchronises every device to it. Read a message on your phone and it shows read on your laptop; delete it in webmail and it disappears everywhere. For anyone using more than one device — which in 2026 is everyone — IMAP is the correct choice.
POP3: The Legacy Download Protocol
POP3 (Post Office Protocol) downloads messages to one device and, by default, removes them from the server. It made sense on dial-up connections decades ago. Today it mainly causes grief: mail trapped on one old office PC, nothing on the phone, and no server copy when that PC fails. Choose POP3 only for the rare single-device archive scenario.
The Ports That Matter
| Protocol | Secure port | Encryption |
|---|---|---|
| SMTP | 465 or 587 | SSL/TLS or STARTTLS |
| IMAP | 993 | SSL/TLS |
| POP3 | 995 | SSL/TLS |
Always use the secure ports. Some Nepali ISPs block port 25 for outgoing mail to reduce spam — another reason 465 or 587 is the right SMTP choice.
Common Errors Decoded
- Cannot connect to server: wrong hostname or port — copy settings exactly from your provider.
- Authentication failed: username must usually be the full email address, not just the name before @.
- Can receive but not send: SMTP authentication is off, or the ISP blocks the port — switch to 587 with STARTTLS.
- Mail differs between devices: one device is on POP3 — convert it to IMAP.
Why Port 25 Gets Blocked and What That Actually Means for You
Port 25 is the original, unencrypted SMTP port used for server-to-server mail relay across the internet — it is also the port historically abused by spam-sending malware on infected home computers, which is why residential and mobile ISPs worldwide, including in Nepal, commonly block outgoing traffic on it by default as a spam-prevention measure. This block was never meant to affect legitimate mail client setups, since properly configured email software has used the authenticated, encrypted submission ports (587 or 465) instead of raw port 25 for over a decade. If a mail client setup is failing specifically on port 25, the fix is simply switching to 587 or 465, not troubleshooting the ISP block itself.
Frequently Asked Questions
Does IMAP fill up my server storage?
Yes, since mail lives on the server — manage it with folders, archiving and sensible quotas rather than by switching to POP3.
What is Exchange or ActiveSync then?
A Microsoft synchronisation technology that bundles mail, calendar and contacts — used by Microsoft 365 and some premium platforms in place of IMAP.
Can I switch a device from POP3 to IMAP without losing mail?
Usually yes, but the process differs by client and any mail already downloaded and removed from the server via POP3 will need to be manually re-added or migrated — worth backing up the local mail file before switching.
Struggling with settings? Our business email plans come with guided device setup — ask the WebsNP team for help.
