IMAP (Internet Message Access Protocol) is how an app reads a mailbox that stays on the server: folders, read status and messages stay in sync across every device. Sending uses a different protocol, SMTP.
Settings
An IMAP host such as imap.gmail.com, port 993 (encrypted), and the same login as the mailbox.
Why cold email tools need it
- Replies: the tool reads incoming mail to spot replies, stop the sequence for that lead and bring the reply into one inbox.
- Bounces: bounce messages arrive in the mailbox and are read the same way.
- Warm-up: warm-up needs to find its emails, move them out of spam and mark them as important.
A mailbox connected for sending only would leave campaigns blind to replies, so tools ask for SMTP and IMAP together. Some providers switch IMAP off by default: for Microsoft 365 an admin turns it on per mailbox; Gmail needs it enabled in settings.