POP3 Mail Collection is when VPOP3 will collect mail from an external POP3 mailbox - for instance, from an Internet Provider.
This page tells VPOP3 how to collect mail.
If the maximum message size is exceeded, VPOP3 will send a message to the intended recipient(s) asking if they want to download the message. If they reply to that message, VPOP3 will download the message at the next scheduled connection as long as the message was not first seen over 14 days ago
Leave Messages On Server is set too large, you may get problems with the mailbox at your mail service provider filling up. If it is set to 0, then VPOP3 will delete the messages immediately after download - however, if the connection is dropped before VPOP3 can successfully log off the remote POP3 server, that remote server will automatically undelete any messages which were deleted during this session.
Like other mail software, VPOP3 uses the
UID values of messages to determine whether the messages have been downloaded before.
UIDs are set by the remote POP3 server.
There are two situations where this can cause problems:
UIDs too quickly, you may get missed messages. For instance, if VPOP3 downloads message '1', deletes it, then logs on again and sees message '1' again, it may think that the ISP failed to delete the message for some reason, so will not download it. In fact, it may have arrived between the two login attempts. If VPOP3 is the only software collecting mail from the ISP, then this problem can be alleviated by setting
Hold Obsolete UIDLs for x Daysto 0 days on the Settings -> Misc Settings -> Advanced page. However, it is really a badly behaving POP3 server at your ISP, so it should be reported to them
UIDs to existing messages, you may get duplicate messages. If you tell VPOP3 to delete messages immediately, that should fix this problem. Note that the POP3 standard explicitly says that this should not happen, so if it happens frequently, it is usually a sign of a problem at the ISP, or someone there not understanding the standards properly, and it should be reported to them. (See section 7 [UIDL] of RFC 1939)
VPOP3 has five different ways of handling mail it collects using POP3
The Routing Errors tab is only visible if the POP3 Routing option is set to Route by parsing message headers.
The Routing Errors tab settings tell VPOP3 what it should do if it receives a message and, after parsing the message headers, it cannot work out who the message is for. Common reasons for routing errors are if the recipient address is misspelled, so that VPOP3 does not recognise it, or if the message was sent using a BCC, so VPOP3 cannot detect any recipients in the message header at all.
The main choice is what to do with the incoming message which it can't handle automatically
There are a couple of extra options
Note that sending a bounce message to the sender can cause backscatter, so is usually a bad idea.
The Messages tab lists all the messages which VPOP3 has seen on the ISP's POP3 mailbox.
Using this list you can tell VPOP3 to re-download or delete some messages, or during its normal download connection.