Deleting Messages from the Server
How and when to delete messages from the POP3 server depends
largely on the objectives of your applications. Some POP3
applications delete the messages as soon as they are downloaded.
These applications typically store a copy of the messages locally
and thus there is no need to keep them on the server.
However, removing messages from the server and storing them
locally will make them unavailable from any computer other than
the one that retained the local copy.
For this reason, many newer POP3 applications do not delete the
message from the server, until you delete it from the local store.
Some applications, such as web based e-mail, do not delete the
message or store a local copy. The message is downloaded
into memory each time it is accessed. This enables the same
messages to be easily accessed from different computers such as
one at work and one at home.
The
EasyMail
POP3 object enables you to delete a
message from the POP3 server in many different ways. Here are some examples:
Delete a message from the server by its ordinal position:
'delete the message from the server
'where x is the messages ordinal position
'of the message on the server
objPOP3.DeleteSingleMessage(x)
If the message you want to delete is in the POP3.Messages
collection, you can delete it from the server like this:
'delete the first message in the Messages
'collection from the server
objPOP3.Messages(1).DeleteFromServer
You can also mark messages for deletion when they are
downloaded with DownloadMessages() by passing in a 2 as the only
parameter to the method:
objPOP3.DownloadMessages(2)
When a message is deleted from the server, the server flags the
message for deletion but does not physically delete the message
until the session is terminated. The RollBack() method of the
EasyMail
POP3 object can be called prior to ending the session to
un-flag the messages so they will not be deleted when the session
ends.
Five things you can not do with POP3
POP3 is an effective, yet simple protocol. Because it is
simple, it will not do everything that you might want to do with
your mail system. Many of the limitations may be bridged by
clever programming, but it is important to understand that they
are not a part of the POP3 protocol. I talk to lots of
developers who are frustrated because they can not figure the
command to do some operation on a POP3 server. Many times
the simple answer is that the command does not exist. POP3
has a very limited command set.
| Create Folders on
the Server |
The POP3 protocol
supports only one folder, the Inbox. Clients such as
Outlook Express enable users to manage a local store of
downloaded messages on their hard drive, but it is important
to understand that this is not a function of POP3. If
you want your application to store and manage downloaded
messages, check out the
EasyMail MailStore object. |
| Have two users
logged into one mailbox at the same time |
The POP3 server will
only allow one user to be logged in to a mailbox at one time.
It is important to properly disconnect from the POP3 server,
or the mailbox may remain locked until a timeout occurs on the
server. |
| Determine if a
message has been read |
The POP3 protocol does not provide a mechanism for the server
to indicate if messages have been read. Clients such as
Outlook Express store data on the local hard drive and thus
can mark those messages as read or unread in the local store,
but not on the server. |
| Determine if there
are new messages on the server |
The POP3 protocol
does not provide a mechanism to enable servers to indicate the
number of new messages on the server. Your
application can store data locally and thus programatically
determine the number of new messages on the server. If
you want your application to store and manage downloaded
messages, check out the
EasyMail MailStore object. |
| Sort the messages |
The POP3 server orders messages from oldest to newest.
The POP3 protocol does not support a mechanism to sort
messages on the server. Many applications simulate this
by downloading the messages and then sort them locally prior
to displaying them to the user. |
Next, bonus information on how to store, organize and manage
downloaded messages on the local hard drive...
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