Because the load operation is really a socket operation, PyMailGUI automatically connects to your email server using whatever connectivity exists on the machine on which it is run. For instance, if you connect to the Net over a modem and you’re not already connected, Windows automatically pops up the standard connection dialog. On a broadband connection, the interface to your email server is normally automatic.

After PyMailGUI finishes loading your email, it populates the main window’s scrolled listbox with all of the messages on your email server and automatically scrolls to the most recently received message. Figure 15-9 shows what the main window looks like after resizing; the text area in the middle grows and shrinks with the window.

Technically, the Load button fetches all your mail’s header text the first time it is pressed, but it fetches only newly arrived email headers on later presses. PyMailGUI keeps track of the last email loaded, and requests only higher email numbers on later loads. Already loaded mail is kept in memory, in a Python list, to avoid the cost of downloading it again. PyMailGUI does not delete email from your server when it is
loaded; if you really want to not see an email on a later load, you must explicitly delete it.

Entries in the main list show just enough to give the user an idea of what the message contains—each entry gives the concatenation of portions of the message’s “Subject:”, “From:”, “Date:”, and other header lines, separated by | characters and prefixed with the message’s POP number (e.g., there are 19 emails in this list). Columns are aligned by determining the maximum size needed for any entry, up to a fixed maximum, and the set of headers displayed can be configured in the mailconfig module. Use the horizontal scroll or expand the window to see additional header details.

Figure 15-9.  PyMailGUI main window resized

As we’ve seen, a lot of magic happens when downloading email—the client (the machine on which PyMailGUI runs) must connect to the server (your email account machine) over a socket and transfer bytes over arbitrary Internet links. If things go wrong, PyMailGUI pops up standard error dialog boxes to let you know what happened. For example, if you typed an incorrect username or password for your account (in the mailconfig module or in the password pop up), you’ll see the message in Figure 15-10. The details displayed here are just the Python exception type and exception data.