IMAP vs POP3 for Developers: Ports, Commands, and Test Scripts

openssl s_client -connect imap.smtp.dev:993 -crlf -quiet

a1 LOGIN qa@test.example.com your-password
a2 LIST "" "*"
a3 SELECT INBOX
a4 UID SEARCH UNSEEN
a5 UID FETCH 1 (FLAGS BODY.PEEK[HEADER.FIELDS (FROM TO SUBJECT DATE)])
a6 UID FETCH 1 BODY[]
a7 UID STORE 1 +FLAGS (\Deleted)
a8 EXPUNGE
a9 LOGOUT

openssl s_client -starttls imap -connect imap.smtp.dev:143 -crlf -quiet

openssl s_client -connect pop.smtp.dev:995 -crlf -quiet

USER qa@test.example.com
PASS your-password
STAT
LIST
UIDL
TOP 1 0
RETR 1
DELE 1
QUIT

# IMAP: UIDs of unread messages
curl "imaps://imap.smtp.dev/INBOX" --request "UID SEARCH UNSEEN" \
  --user "qa@test.example.com:$QA_PASSWORD"

# IMAP: the message with UID 1, raw
curl "imaps://imap.smtp.dev/INBOX;UID=1" --user "qa@test.example.com:$QA_PASSWORD"

# IMAP: only its headers
curl "imaps://imap.smtp.dev/INBOX;UID=1;SECTION=HEADER" \
  --user "qa@test.example.com:$QA_PASSWORD"

# POP3: list the messages, then fetch the first
curl "pop3s://pop.smtp.dev/" --user "qa@test.example.com:$QA_PASSWORD"
curl "pop3s://pop.smtp.dev/1" --user "qa@test.example.com:$QA_PASSWORD"

import email
import imaplib
import os
import ssl
import time
from email import policy


def wait_for_message(to, timeout=30):
    with imaplib.IMAP4_SSL("imap.smtp.dev", ssl_context=ssl.create_default_context()) as imap:
        imap.login("qa@test.example.com", os.environ["QA_PASSWORD"])
        imap.select("INBOX", readonly=True)
        deadline = time.monotonic() + timeout
        while time.monotonic() < deadline:
            _, data = imap.uid("SEARCH", "TO", f'"{to}"')
            uids = data[0].split()
            if uids:
                _, parts = imap.uid("FETCH", uids[-1], "(BODY.PEEK[])")
                return email.message_from_bytes(parts[0][1], policy=policy.default)
            time.sleep(2)
    raise TimeoutError(f"no message to {to} after {timeout}s")


message = wait_for_message("qa+run42@test.example.com")
print(message["Subject"])
print(message.get_body(preferencelist=("plain",)).get_content())

with imap.idle(duration=30) as idler:
    for kind, data in idler:
        if kind == "EXISTS":
            break

import os
import poplib
import ssl
from email import message_from_bytes, policy

pop = poplib.POP3_SSL("pop.smtp.dev", context=ssl.create_default_context())
pop.user("qa@test.example.com")
pop.pass_(os.environ["QA_PASSWORD"])

count, size = pop.stat()
for number in range(1, count + 1):
    _, lines, _ = pop.top(number, 0)
    headers = message_from_bytes(b"\r\n".join(lines), policy=policy.default)
    if "qa+run42@test.example.com" in headers.get("To", ""):
        _, lines, _ = pop.retr(number)
        message = message_from_bytes(b"\r\n".join(lines), policy=policy.default)
        print(message["Subject"])
        print(message.get_body(preferencelist=("plain",)).get_content())
        break

pop.quit()

import { ImapFlow } from 'imapflow'
import { simpleParser } from 'mailparser'

const client = new ImapFlow({
  host: 'imap.smtp.dev',
  port: 993,
  secure: true,
  auth: { user: 'qa@test.example.com', pass: process.env.QA_PASSWORD },
  logger: false,
})

await client.connect()
const lock = await client.getMailboxLock('INBOX')
try {
  const uids = await client.search({ to: 'qa+run42@test.example.com' }, { uid: true })
  const { source } = await client.fetchOne(uids.at(-1), { source: true }, { uid: true })
  const message = await simpleParser(source)
  console.log(message.subject, message.text)
}
finally {
  lock.release()
}
await client.logout()

await client.mailboxOpen('INBOX')

client.on('exists', ({ count, prevCount }) => {
  console.log(`${count - prevCount} new, ${count} in the inbox`)
})