For the technologically challenged, what is a sequential file, what is its significance, and how does one clean it up?
Most email programs don't actually delete a message: they just move it to another folder.
All you have to do is empty your Trash folder, or the Deleted Items folder, or whatever your email client calls it.
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If you go into your system with something like old Norton Commander or even a wordprocessor, you can find your mail files. You will see some fascinating things. First off, there is an enormous amount of overhead in your mail that is not seen. It's much like looking at a HTML file in HTML for rather than text form. When you receive email the mail is added to one long file in something similar to a single word processor text file which may run megabytes long. Because of the format of the file and the continuing nature, it is a sequential file. In the old days using Netscape three I would collect email files as much as six megabytes long on the disk. Also, unless you telly your browser to erase received emails, the same file will be saved in your ISP computer. I ran up over ten megs at my ISP until they notified me and I had them erase it. We then adjusted my Netscape system to erase files at the ISP as I received them.
There is some provision for deleting deleted email files on your disk. What I have also done is rename my email files, then go into them with a word processor and delete all the deleted messages. Netscape email will start a new email file. It's rather complicated. I have email archives saved as word processor text files.