The POP3 Client Lua Script is called POP3CLT.LUA and is edited in Settings → Scripts. This script is called whenever VPOP3 runs a POP3 session to download messages from a remote POP3 server.

VPOP3 will call the following Lua functions in the script at the following times:

• Start() - called when the POP3 session starts, before VPOP3 starts downloading any messages.
• DownloadRules() - called before each message is downloaded to determine how VPOP3 should handle the message. A scripted version of normal Download Rules in VPOP3.
• StartMessage() - called just before VPOP3 starts downloading a message from the remote server.
• MessageLineRaw() - called when VPOP3 has downloaded a line of a message from the remote server.
• MessageLine() - called after VPOP3 has processed a line of a message from the remote server,just before it saves it.
• EndMessage() - called when VPOP3 has finished downloading a message from the remote server.
• ProcessMessage() - called after VPOP3 has downloaded a message from the remote server to determine if any special actions need to be performed on the message.
• End() - called at the end of the POP3 session.

ProcessMessage(“<mailfrom>”, “<subject>”, <recipient list>, <current actions>, <message MIME structure>, <message size>, <attachments>)

This function is called by VPOP3 when a message has been received by the SMTP service.

• <mailfrom> is the SMTP 'MAIL FROM' address
• <subject> is the message subject line
• <recipient list> is a table containing a list of the recipient email addresses (from the RCPT TO envelope)
• <current actions> is a table with the following entries
  • SendToOriginalRecipients boolean - should the message be sent to the originally specified recipients
  • Delete boolean - should the message be deleted after retrieving
  • Ignore boolean - should the message be ignored
  • Reason string - text string to use if a reason is needed for the action
  • Recipients table - table containing new/replacement recipients for the message
  • HeaderModifiers table - list of message header modifications to make
• <message MIME structure> is a table with one or more of the following entries
  • Path string - the IMAP style path to the message section
  • ContentType string - the main content type (eg 'text', 'image' etc)
  • ContentSubtype string - the content subtype (eg 'html', 'plain', 'gif', etc)
  • ContentTypeFilename string - the filename from the ContentType header
  • ContentDisposition string - usually 'inline' or 'attachment' or blank
  • ContentDispositionFilename string - the filename from the ContentDisposition header
  • Start number - the offset from the start of the message where this section starts
  • End number - the offset from the start of the message where this section ends
• <message size> is the size of the message in bytes
• <attachments> is a table with zero or more of the following entries, referring to the attachments in the message
  • MIMESection number - the MIME section that this attachment occurred in
  • Name string - the name of the attachment
  • MIMEType string - the MIME type of the attachment
  • Size number - the size of the attachment
  • Type string - the type of attachment (MIME, UUE, BINHEX, MIMEUUE, MIMEBINHEX, TNEF)

This function should return <new actions table>, <results string>

In this function the VPOP3 ProcessMessage helper functions can be used.