I have Thunderbird as my client on my primary home workstation as well as my traveling laptop. Each instance is configured exactly the same with regards to the four servers I use: Earthlink, GMail, Outlook and GMX. Each of those server/services is also identically configured with regards to these Server Settings: Leave Messages on the Server Until I Delete Them. Each of the servers -- except GMail -- has the same behavior with regards to how it handles things when I click on the option to Get Messages, i.e., each server seems to be able to identify which of the clients has and which of the clients has not previously been served up with a newly arrived email. It will not send the same email to the same client more than once. GMail is the exception. There I get what seems to be a first-come-first-served protocol. If I perform Get Messages on the laptop, I will get the email, but will not be able to get the email when I subsequently make the request from the workstation's Thunderbird instance. [Or, if the first request is made from the workstation instance, the laptop instance will never get the email.] I realize that my usage pattern is rather unique, so it may well be that no one else has ever experienced this behavior, but if anyone has -- with regards to any email server, not just GMail -- and knows a work-around, I would appreciate the instruction. And, in anticipation of one line of questioning, when I say that all four server/services are configured the same, I am indicating that I do work with GMail as a POP3 server, not IMAP. All my email content ultimately resides on my own hardware resources and is only temporarily resident on hardware provided by the server/service entity. P.S. Please pardon my mistake in initially, mistakenly posting this request to the Firefox community.