Why is Mail unable to receive my emails when other mail programmes can?

Question

I use Mail 2.1 on my Macbook (OSX 10.4.8) and Mail 1.3.11 on my G5 iMac (OSX 10.3.9). As of the last 36 hours, I can send email, but not receive it, and this is the case on both computers.If I use Thunderbird,or Eudora - no problem.
I haven't changed any settings, or made any adjustments to my accounts on Mail.
Web connectivity is fine, and as I say, I can send emails using Mail.These are POP accounts (sending is SMTP).
Does anyone have any ideas?
G5. 1.8Ghz Mac OS X (10.3.9) MacBook 2Ghz Intel Core Duo Mac OS X (10.4.8)
G5. 1.8Ghz Mac OS X (10.3.9) MacBook 2Ghz Intel Core Duo Mac OS X (10.4.8)

Answer 1

I didn’t realize you had posted in both the Mac OS X 10.3 and Mac OS X 10.4 forums. I’ll repeat here my reply there with some additional questions that apply to Mail 2.x only.
What’s the problem exactly? Is it that Mail checks for mail but downloads nothing, or that it doesn’t even attempt to download, or what?
Go to Apple Menu > System Preferences > Network, choose Network Port Configurations from the Show popup menu, and make sure that the configuration used to connect to Internet appears at the top of the list.
In Mail, open Window > Connection Doctor. What does it say?
Could it be that Mail or this particular account is in an “offline” state? Is the Mailbox > Go Online command enabled or disabled?
Go to Preferences > Accounts > Advanced. Is Include when automatically checking for new mail ON or OFF?
What’s the time interval chosen in Preferences > General > Check for New Mail?
Open the Account Info window by choosing Get Info (⌘I) from the Action menu (gear icon) located below the mailboxes list in the main Mail window. Does Mail display there the messages that it doesn’t download? Do they appear as already downloaded or as not downloaded yet (dot column)?