Suddenly Blocking POP3??

I have a WIERD problem this afternoon.

Alas, everything always has to break down Friday afternoon so as to postpone my weekend as long as possible. :( [/whine]

No one can check POP3 mail all of a sudden. We can receive mail, and we can access mail via web control panel, but we cannot receive any mail via a mail client (thunderbird, outlook, etc.). I get a "connection refused" error. This only began within the last hour.

Firewall log shows this:

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12/09/2005 16:27:49.736 TCP connection dropped
Source: 192.168.1.12, 3836
Destination: LAN 64.39.51.10, 110, WAN
'Retrieve Email (POP3)'

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That appears every time I get a "connection refused" error trying to check mail. But why is this being dropped at the firewall? I haven't made any configuration changes to the firewall (SonicWALL SOHO3), and it was set up to allow POP3 to slide right on in, as it has been all along. For some reason, within the last hour or so, it just decided it doesn't want to anymore.

So I'm rather lost on this one. Any ideas?

Since your post lacks some detail... ;)... I'll postulate..... Though your post is confusing...

Oddities:-

You say you can receive email and access mail via web.... How are you receiving that email other than via the web? IMAP?

Questions:-

1. Do you have your own mailserver in a DMZ or are you hosted by a third party?

2. Your firewall seems to be telling you that the connection was "dropped". This could mean that the connection received an RST from the remote, (I'm not familiar with Sonicwall logs), and the fact that you get a "connection refused" at the client implies that, rather than receiving no response - therefore a "connection failed" error it understands that the connection was "refused". Has your third party decided to cut off POP access to their server?

3. If you host yourself and have changed nothing have you tried to restart the POP service on the server. Sometimes SMTP and POP will lock up because some "sweet" person has sent the entire contents of their My Documents folder home so they can be more efficient and work on stuff on the weekends... regardless of the fact they have been employed there for 15 years and have 8.6Gb of crap in that cute "My Documents" folder..... Been there, seen it.... :rolleyes: You need to be quite quick to check the POP mail after the restart otherwise the "sweet" persons machine will lock you up again....

As an aside... POP never "slides right on in". POP is a "pull" protocol... Thus it slides right on _out_ not in.... The SYN goes from the client out through the firewall.... SMTP "Slides right on in" because it is a "push" protocol..... Just trying to maintain the accuracy around here.... ;)

U:\>nc -vv -n 64.39.51.10 110
(UNKNOWN) [64.39.51.10] 110 (?) open
+OK <37342.1134170246@gideon.swishmail.com>

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No one can check POP3 mail all of a sudden.

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Sounds like the POP3 server is down.

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We can receive mail, and we can access mail via web control panel, but we cannot receive any mail via a mail client (thunderbird, outlook, etc.). I get a "connection refused" error. This only began within the last hour.

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When you attempt to recieve email using Outlook what error number do you get? It should start with 0x888cccxx something? Have you tried clearing the outbox? Also, deleting and rebuilding e-mail account? Have you tried using Putty to see if you can duplicate the issue? Send your self a test message within outlook? Just to generate an error number.

How about your AV, does it have POP scanning, I know Trend Micro has a habit of replacing the POP server account name with localhost, and we have to reset the account.... ;)

As TS has said, your connection is being refused so the server you are trying to connect to for some reason is not allowing you to. Hence this is almost certainly a fault/problem at the other end

My first thought was a user name/pass word error in outlook but that generates a authentication error not a connection error.

Is the server part of your domain or is it an external one?

If it is external have a check with who ever runs it to see if the have upgraded the security of it, i.e. Secure Password Authentication or the have decided it needs a SSL connection. If they have you will have to change your mail account settings in Outlook.