POP3/IMAP Configuration Settings

Adding POP3/IMAP Accounts

Each external mailbox that POPcon should retrieve mail from is configured as an individual POP3 or IMAP account. Add as many accounts as needed — POPcon processes them sequentially during each mail retrieval cycle.

Accepted Recipient Domains

For catch-all mailboxes, configure one or more accepted recipient domains. POPcon uses these domains to filter incoming messages: only emails addressed to recipients within the listed domains are forwarded to the internal mail server. This prevents unrelated messages from being delivered when the external mailbox collects mail for multiple domains.

Max Emails per Download Pass

Set the maximum number of emails POPcon retrieves from an account in a single download pass. This limit helps control bandwidth and processing time, particularly for accounts that accumulate a large volume of messages between retrieval cycles.

Server Types and Port Numbers

POPcon supports the following server types for connecting to external mail providers (which one to pick per provider, and how the encryption setting and the port belong together, is explained in the guide POP3 or IMAP for retrieving provider mailboxes into Exchange?):

• POP3 — standard POP3 connection (default port 110).
• POP3-SSL — POP3 over SSL/TLS (default port 995).
• IMAP — standard IMAP connection (default port 143).
• IMAP-SSL — IMAP over SSL/TLS (default port 993).

The SSL ports 995 and 993 expect the connection to be encrypted before the first command (implicit TLS); on 110 and 143 the connection starts in plain text and can be upgraded with STARTTLS. Which encryption value belongs to which port, and the error a mismatch produces, is explained in the guide POP3/IMAP over TLS for mail retrieval: ports 995 and 993, STARTTLS vs implicit TLS.

Access Settings

Each account requires the following access parameters:

• Server name — the hostname or IP address of the external mail server.
• Username — the login name for authenticating with the mail server.
• Password — the corresponding password for the account.
• Port — the TCP port number (defaults depend on the selected server type).
• Timeout — the number of seconds POPcon waits for a server response before treating the connection as failed.

Mailbox Types

POPcon distinguishes between two mailbox types:

• Catch-all mailbox — collects mail for multiple recipients. POPcon examines message headers to determine the intended recipient and delivers each message to the corresponding internal mailbox. A re-route address can be configured to receive messages whose recipients cannot be resolved.
• Single-user mailbox — all mail retrieved from this account is delivered to one specific internal recipient, regardless of the addresses in the message headers.

Which type suits your provider and your users, including the BCC and mailing-list cases, is compared in the guide Catch-all (multidrop) mailbox vs one POP3 mailbox per user.

Delete / Keep Email Options

After downloading messages, POPcon can handle mail on the remote server in one of the following ways:

• Delete emails from server — messages are removed immediately after successful download.
• Leave emails on server indefinitely — messages remain on the remote server and are not deleted by POPcon.
• Leave emails on server for N days — messages are kept on the remote server for the specified number of days, then deleted. This provides a window for other clients to retrieve the same messages.