Question 1

What is the difference between IMAP and POP?

Accepted Answer

**POP downloads mail to one device; IMAP keeps mail on the server and synchronises.** For anyone using more than one device, IMAP is the correct answer and POP is a source of confusing problems.

**POP3** was designed for a world of one computer and an occasional dial-up connection. It connects, downloads new messages, and by default **deletes them from the server**. Everything then lives on that one machine. Read status, folders and deletions are local and invisible to anything else.

**IMAP** keeps the authoritative copy on the server. Clients display a synchronised view: read a message on your phone and it shows as read on your laptop; file it into a folder and the folder exists everywhere; delete it and it is gone from all devices. Messages are downloaded on demand or cached.

**What this explains:**

**"My old emails vanished from my phone."** POP on a computer downloaded and removed them from the server.

**"I deleted it on my laptop and it came back."** Mixed configuration, or a client with a leave-on-server setting.

**"My mailbox is full but my computer has plenty of space."** IMAP storage is the server's quota, not your disk.

**When POP is still defensible:** archiving mail off a server with a tiny quota; a single device with no synchronisation requirement; and retaining a local copy of a mailbox you are about to lose access to.

**Why both are being superseded.** Major providers increasingly prefer proprietary synchronisation protocols or **Exchange ActiveSync**, which also sync calendars and contacts — something neither IMAP nor POP does. Both are also being restricted for security: **basic password authentication is being disabled** in favour of OAuth, which is why older mail clients suddenly stop connecting and require an app password or reauthorisation.

**Sending is separate.** Neither protocol sends mail — that is **SMTP**, configured independently, which is why an account can receive and fail to send.

**If migrating**, use IMAP on both ends so folders and read status transfer rather than downloading and re-uploading.

Question 2

How does an email actually get delivered?

Accepted Answer

Through a chain of servers using SMTP, guided by DNS — and the important structural fact is that email is a store-and-forward system with no guarantee of delivery and no reliable confirmation of

Question 3

What is a point of presence?

Accepted Answer

A point of presence (PoP) is a physical location where a network has equipment that other networks or customers can connect to — the places where an abstract "network" actually touches the ground.

Question 4

What happens when you send a text message?

Accepted Answer

It travels through the signalling channel of the mobile network rather than as ordinary data — a design accident from the 1980s that explains almost everything odd about SMS. The origin. SMS was

Question 5

What is a MAC address, and how is it different from an IP address?

Accepted Answer

A MAC address identifies a piece of hardware on a local network; an IP address identifies a location on the internet. One is fixed to the device, the other describes where the device currently is —

Question 6

What is actually inside a network packet?

Accepted Answer

Layers of headers wrapped around your data, each added by a different part of the networking stack and each read by a different piece of equipment along the way. Why layers exist. Each layer solves

Question 7

How does roaming work when you land abroad?

Accepted Answer

Your phone attaches to a foreign network that has an agreement with your own, and your home network continues to authenticate you and to control what you can do — which is why your number, your

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