Training the Next Generation of IT Engineers
And with the magical incantation, “XNR8HKBGANTP”! InetDaemon was added to the Technorati blog list… Just how do you pronounce that?
(Jump Straight to The Fix)
All of a sudden, you can’t send or receive e-mail.
Why?
Your mailbox may be full.
Your computer doesn’t actually send and receive e-mails directly. Your mail client software, either Microsoft Outlook, Mozilla Thunderbird, SeaMonkey, Apple Mail etc. will send and receive mail via the Internet’s version of the local post office, your Internet service provider’s mail server. Your provider sets aside storage space on their servers to store mail while you are not connected to it (when your mail software isn’t running). Most providers have a limit of how much mail you can store on their servers, and the mail stored on their servers. If your provider offers webmail as a service, only the mail stored at the provider’s servers will be visible in your mailbox.
When this storage space at the servers is used up (full) you cannot send or receive any more e-mail until you delete something. It’s more or less the same as having a post office box at the post office, and the box being too full to cram any more letters into. Periodically, you have to go to the post office and empty it. Big parcels will fill the box faster than small letters. With e-mail, the big parcels are e-mails with attachments, or e-mails with pictures or video embedded in them. The bigger the mail messages are, the faster the mailbox fills up. Consider carefully what you send and receive.
Let me show you how to fix this…
(Jump straight to The Fix)
The Reader’s Question:
Dear InetDaemon,
Why do I get a “503 Valid RCPT command must precede DATA” message when I send to some people?
Thanks!
The Error Message
This mail message is sent to you automatically by the mail server. It most often happens when you are sending to someone who doesn’t use the same mail provider you use. The mail server will automatically send you this notification when you have not configured Outlook to send your login information to the server before sending e-mail. The body of the notification email will have a message that looks something like this:
FROM: System Administrator
TO: InetDaemon
Subject: Undeliverable: Test Message
Your message did not reach some or all of the intended recipients.
Subject: Test Message
Sent: 6/2/2012 7:38 AM
The following recipient(s) cannot be reached:
<address@domain.tld> on 6/2/2012 7:38 AM
503 Valid RCPT command must precede DATA
Why It Happens
Responsible email providers will require you to configure Outlook to log in to their server before sending e-mail to restrict the ability to send mail from their servers to just their own customers. This helps block spam by preventing anyone who doesn’t have a login from sending an e-mail from that server. Your mail service provider requires that you verify your account information before downloading mail (via IMAP or POP3), and they also require it before sending mail via Simple Mail Transfer Protocol (SMTP).
Sending login information to the server before sending an e-mail is not a Microsoft Outlook default, so you get an error from your email provider’s mail server when sending to external providers.
The Geeky Bits
The mail server that actually sends your e-mails for you has been configured to use the SMTP AUTH extension as defined in RFC 2554. When sending an e-mail, the mail user agent (Outlook) connects to the mail transfer agent (your provider’s mail server) and the server responds with the authentication types used by sending the client the SMTP verb “AUTH” and a list of methods. The client selects an authentication method it supports and replies back with “AUTH <method>”. If the server does not receive an AUTH from the client, it treats the client as an unknown sender and does whatever the server is programmed to do when an unknown sender sends mail (ignore the mail message, send a warning message to the client).
How to Fix It
How to fix “503 valid RCPT command must precede DATA”:
Continue reading
I happen to have the ‘good fortune’ of having more than one Apple Fanboy amidst my network of associates and they are all downplaying the latest round of Flashback-based malware infections on the Mac as being ‘unusual’ and ‘nothing to worry about’ and they still insist that installing anti-malware software is pointless. Same thing they have been telling me for just about a decade.
Contrary to what the Fanboys say, Mac OS X has been hit with viruses and worms in the past. Flashback is not the first. Malware specifically targeting the Mac OS X platform starting appearing as early as 2004. Apple computers have never been ‘immune’ to malware and spyware, contrary to Apple’s advertising, and Apple computers have been part of the earliest history of virus development, beginning with Elk Cloner which predates the first PC virus “Brain” by about 4 years. Yes, owners of Apple products had to worry about viruses four years before PC users did…
Here’s the a small sample of the kinds of malware targeting Apple computers that I could dig up in a quiet evening at home from the web. This list of Apple Malware is far from complete:
- 1982 – Mac Virus Elk Cloner (created by Richard Skrenta). A boot sector virus attacks the Apple II. This predates the first virus on Windows computers, so Apple computers got viruses before PC’s did. Dwindling market share protected the Apple computers–just wasn’t worth the hacker’s effort.
- 1992 – INIT 1984 – Triggers on Friday the 13th on any computer running MacOS (pre-OS X)
- 1994 – Mac Virus INIT-29-B modifies system files and applications, crashes the early Macs.
- 1995 – HyperCard Virus HC-9507 embeds itself in all HyperCard stacks.
- 1987 – nVIR Virus. Spread by infected floppies.
- 1988 – HyperCard viruses start appearing
- 1990 – MDEF (Garfield) infected the operating system files.
- 1998 – Hong Kong / AutoStart 9805 infects via the AutoPlay feature of QuickTime.
- 1998 – Sevendust / 666
- 2004 – OSX /Renepo (opener) script worm
- 2006 – OSX/Leap-A (OSX.Oomp). First ‘official’ Mac OS X virus. Actively infects via iChat buddy lists.
- 2006 – Inqtana worm and virus
- 2006 – Macarena – Proof of Concept worm
- 2007 – BadBunn; also OSX/RSPlug (DNS Changer) – Persisted till 2011 due largely to the myth that Macs are immune, so Mac users did not patch or protect their systems.
- 2008 – MacSweeper scareware, Imunizator scareware
- 2008 – AppleScript.THT that spreads via the Remote Desktop Agent feature by using a tunnel to hide itself from the firewall and allow remote hackers complete access and control of the Mac.
- 2008 – OSX.Lamzev.A – Opens a backdoor to allow hackers to control your Mac remotely
- 2008 – OSX.Trojankit.Malez … Continue reading