Gmail Not Working With leopard Mail

My Gmail account worked perfectly with Mail in Tiger but when I upgraded to leopard and set up the mail account, I get error messages saying that the gmail server rejected my password, its the same with POP, IMAP and SMTP. I would rather stick to POP. I have used the automatic set up and when that didn't work I used the manual setup numerous times and still not working, I know that it is the right username and password because I can log onto emails web mail with it and can confirm that POP access is enabled

I don't really have any insight to your issue, but my Gmail works just fine with Leopard...

More detail, same problem...

I'm having the same issue. I've checked all the settings and followed steps given by Google. Even deleted the account in Mail.app and recreated it following Googles steps.
I found an articles saying to make sure passwords are set in the Mail.app Account tab prefs, and one even walked through blowing away keychains. All have not helped. FWIW, In Tiger running Mail.app 2.x it works fine, but Mail.app 3.x under Leopard, no go. I have other accounts, like .Mac, and other SMTP unix accounts and there is no problem.
I have heard that if you have a iPhone or iTouch accessing your mail it will cause issues. I don't see how this is even plausible but will give it a try.

More detail of the problem:
First launch of Mail.app in Leopard (PPC or Intel is the same) passwords or "lost" or "missing". Go into Mail.app's prefs --> Accounts tab and put password in outbound and inbound password fields. Make sure everything is saved by clicking on General tab. Close the prefs window. Send and receive mail just fine until you quit Mail.app. Launch Mail.app again passwords are "lost" or "missing" again in the Mail.app prefs-->Account tab fields. Mail does not send and receive until you save password again. Check the keychain shows passwords, but their are multi versions of the same keychain. Could this be the root problem? Is Mail.app generating a new keychain every launch? Is it that Mail.app can't read the keychains or the password value is not understood by Gmail due to some kind of encryption?

Just asking. Maybe someone knows. But problem does not exists with SMTP unix mail or .Mac.

To halo:

Try deleting the plist file for mail: (make a backup first)

/Users/your user name/Library/Preferences/com.apple.mail.plist

Regards.

this fixed my problem

I was having the same exact problem. This is what I did to fix it.

erased mail passwords from the keychain
Repair the keychain (under keychain access- keychain firstaid)
logged on to google and changed gmail password. (they now require an 8 letter password)
Opened mail app and re-entered the new password.

Hopefully this works for you too.

Works fine for me. I personally prefer imap. Make sure you have secure settings enabled. TLS It will not work with the unsecure ports.