Error downloading messages - wont download

Question

Hi
In short, TBird (24.5) stopped downloading messages sometime between 321PM Friday, 2 MAY 14 and 522pm Friday, 2 MAT 14. Those messages are now backing up with my ISP.
I use Frontier Communications as my primary ISP and primary email. They used to be strictly POP for email but are now some type of hybrid with their relationship with Yahoo Mail. That 'merger' happened quite awhile ago and I do not believe it has any bearing on this issue. I continue to use POP to download my messages. Also, technically I am connecting thru a Comcast account at this location, but have been doing that for quiet some time as well with no issues.
I did contact my ISP tech support (Frontier) 1 week ago and we went thru all their suggestions to adjust and/or test my TBird settings with no luck. They were at a loss.
So I am currently using TBird 24.5. I upgraded to that one on ~29 APR 14 and had no issues downloading until four days later. I have been using TBird since maybe ~16.0 or 17.0.
I currently get the following error when trying to download messages:
The RETR command did not succeed. Error retrieving a message. Mail server pop3.frontier.com responded: [SYS/TEMP] problem retrieving message.
To me, this error message seems to indicate a problem with Frontiers server's, not TBird, but I am trying anything at this point. And if I can rule out TBird having an issue then maybe I can go back to my ISP with more knowledge.
This is all occuring in the Windows 7 (64bit) environment.
I have read several threads around the community with no luck. I tried moving the first unread message in my webmail (the one that did not download at 520pm 2 MAY) with no effect. I also tried the recreation of the .msf Inbox file with no effect.

Answer 1

I fixed the problem!
After reading back thru several forum chains I came across several ideas - most did nothing. But then one worked!
Ok so to summarize, if you are receiving the error message:
The RETR command did not succeed. Error retrieving a message. Mail server pop3.frontier.com responded: [SYS/TEMP] problem retrieving message. (NOTE: the server name could be any server I presume)
Assumed Cause:
Then what appears to have caused it is that my ISP (who now uses yahoo mail services [this may very well be a yahoo mail server issue as the source I used also mentioned yahoo]) thought I had received a spam message. (When going online to my ISP's webmail I could see all my message, plus three in spam.) It turns out that the oldest message in spam seems to have caused a hang up in downloading all subsequent messages. I guess that the spam folder is part(?) of the Inbox folder or somehow related. Maybe a subfolder mirror?
Solution:
1 - I created a folder in my ISPs webmail called TEST (any name should work).
2 - I then used the webmail's MOVE command to move the three messages in the webmail spam folder into the new webmail TEST folder.
3 - I then tested TBird on my system using it normally and everything downloaded! :)
3a - Strangely, somehow in this process two of the three messages that were in the webmail spam folder that I had transfered into the new webmail TEST folder... disappeared... not sure where.. maybe they downloaded or who knows. The oldest message remained though.
4 - I then copied the message from TEST back into webmail Inbox.
5 - I then tested TBird again and guess what? Got the RETR error again and download would not occur.
6 - So then I deleted that offending message from webmail permanently and now TBird appears to be working just fine.
Other thoughts:
1 - Interestingly, none of the messages in the webmail spam folder were actually spam. Yahoo settings may be too sensitive. I will investigate and see if I can access and/or adjust them for the future.
2 - The email in question may have had some corruption as I could not even open it in webmail.
3 - Also, it had attachments which may or may not have affected the situation. *shrug*
Well I hope this discussion and solution help anyone else dealing with the RETR error.