What Is IMAP?
IMAP (Internet Message Access Protocol) is a standard protocol for reading email stored on a mail server. Unlike POP3, which downloads and often deletes messages, IMAP keeps mail on the server and syncs folders, read status, and flags across every device — making it the default for modern webmail and multi-device access.
IMAP lets an email client view and manage messages that stay on the server. When you read, move, flag, or delete a message, the change is recorded server-side and reflected everywhere you log in. This is why an email opened on your phone shows as read on your laptop — the server holds the single source of truth.
The older POP3 protocol works differently: it downloads messages to one device and, by default, removes them from the server. POP3 suits a single-device, offline workflow, but it does not sync state between devices, which is why nearly all modern providers default to IMAP.
IMAP is a receiving protocol only. Sending email uses SMTP, a separate protocol. A full mailbox connection therefore uses IMAP (or POP3) to read and SMTP to send — and warmup tools need both: SMTP to send warmup mail and IMAP to read the replies.
IMAP vs POP3
The core difference is where your mail lives and whether state is synchronized. IMAP keeps messages on the server and treats your clients as windows onto that server: folders, read/unread status, and flags all sync. POP3 pulls messages down to one device and, in its default configuration, deletes the server copy, so a second device sees nothing and there is no shared state.
For anyone using more than one device — phone, laptop, webmail — IMAP is the correct choice, and it is what Gmail, Outlook, Yahoo, and virtually every modern provider recommend. POP3 remains useful only in narrow cases: archiving everything to a single machine, or working with strict local storage and no need to sync.
How MailPilot uses IMAP
Email warmup works by exchanging real messages between mailboxes: a warmup send goes out, and the receiving mailbox must open it, reply, and rescue it from spam. To detect and act on those exchanges, MailPilot connects to each mailbox over IMAP to read incoming warmup mail — finding the warmup message, marking it important, moving it out of the spam folder, and confirming the reply landed.
That is why connecting a mailbox to a warmup tool requires both IMAP and SMTP credentials: SMTP authorizes MailPilot to send on the mailbox’s behalf, and IMAP authorizes it to read the inbox so it can register opens, replies, and spam-folder rescues. If IMAP is disabled or the credentials are wrong, warmup can send but cannot verify or engage with received mail.
IMAP vs POP3 vs SMTP ports
| Protocol | Purpose | Encrypted port (SSL/TLS) | Legacy / plaintext port |
|---|---|---|---|
| IMAP | Read mail (kept on server, synced) | 993 | 143 (STARTTLS) |
| POP3 | Download mail to one device | 995 | 110 (STARTTLS) |
| SMTP | Send mail | 465 | 587 (STARTTLS) / 25 |
Frequently asked questions
What is IMAP?
IMAP (Internet Message Access Protocol) is a protocol for accessing email stored on a mail server. It keeps messages on the server and synchronizes folders, read status, and flags across all your devices, so a message read on one device shows as read everywhere. It is the modern default for reading email.
What is the difference between IMAP and POP3?
IMAP keeps your mail on the server and syncs its state (folders, read/unread, flags) across every device. POP3 downloads messages to a single device and, by default, deletes the server copy, so it does not sync between devices. IMAP is preferred for multi-device access; POP3 suits single-device, offline use.
What port does IMAP use?
IMAP uses port 993 for secure connections over SSL/TLS, which is the recommended setting. The older plaintext port 143 (upgraded to encryption with STARTTLS) also exists but should be used with TLS. Most providers require the secure port 993 for reliable, encrypted access to your inbox.
Why does email warmup need IMAP access?
Warmup tools use IMAP to read a mailbox’s incoming mail so they can engage with it — opening warmup messages, replying, and rescuing them from spam. SMTP only lets a tool send; IMAP lets it verify and act on received mail. Without IMAP, warmup can send but cannot generate the engagement signals that build reputation.
MailPilot connects to each mailbox over IMAP (port 993) and SMTP to send warmup mail and read the replies, automatically opening, replying to, and rescuing warmup messages so your domain earns real positive engagement.
See how MailPilot connects mailboxes →