Mail on the laptop, gone from the phone
Sofia reads her work email on her laptop. Later she opens her phone, and the messages are not there. The laptop took them and removed them from the server.
One wrong setting caused it. The right setting would have kept her mail in both places.
Key words
| Word | What it means |
|---|---|
| Protocol | a set of rules that computers follow to talk to each other |
| POP3 | a protocol that downloads email from the server to one program |
| IMAP | a protocol that keeps email on the server and shows it to many devices |
| SMTP | a protocol that sends email and passes it between mail servers |
| S/MIME | a standard for sending encrypted and signed email |
| Port | a numbered door on a computer that a service listens at |
| SSL | an older way to make a connection secure |
| TLS | the newer way to make a connection secure, which replaced SSL |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say what POP3, IMAP, SMTP, S/MIME, ports, SSL and TLS do, and set up a mail account.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Getting mail: POP3 and IMAP
POP3 downloads mail from the server to a program on one device. The mail is usually removed from the server after. It suits one PC with a small mailbox.
IMAP keeps the mail on the server. Each device shows what is on the server. A message read on the phone shows as read on the laptop. It suits people with many devices.
Sending mail: SMTP
SMTP sends mail. Your mail program hands a message to your mail server by SMTP. Then the servers pass it on, by SMTP too, until it reaches the mail server of the person you wrote to.
So a mail account needs two sets of settings: one to get mail (POP3 or IMAP) and one to send it (SMTP).
The three protocols and their ports
| Protocol | Job | Normal port | Secure port |
|---|---|---|---|
| POP3 | Download mail to one program | 110 | 995 |
| IMAP | Read mail kept on the server | 143 | 993 |
| SMTP | Send mail and pass it between servers | 25 (server to server) | 587 with TLS, or 465 |
The cells students fill in are left blank in this preview.
Look up standard port names
grep -E '^(smtp|submission|pop3|pop3s|imaps)[[:space:]]' /etc/servicesA command for the lesson’s lab terminal. It is shown here and not run.
Check: the protocols
Have a go
Check: the protocols
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.