Removing email proxy addresses from AD (helpful if you sync your AD to Office365)

Right now, this is a partial post while I get the PowerShell scripting components together. I needed to remove all the proxy addresses for a certain domain in advance of removing that certain domain from our Office365 account. Because we sync our local AD with Office365, I need to remove the proxy addresses from the local AD.  I could do this manually, of course - which is long and inefficient.  The crucial command I used is this one:

Set-ADUser username -Remove @{ProxyAddresses="smtp:username@domain.com"}

I ran this from "Active Directory Powershell for Windows PowerShell"

Because I'm not good enough with PowerShell yet, here's what I did.  I tried to remove the domain from the account in Office365.  Office365 returned all the mailboxes that had the domain as aliases.  I copied and pasted the list of mailboxes to Excel.  I extracted the mailbox user names from the list and made a single column in Excel of those mailbox names (in my case - our domain uses a username of joe.smith as the username for Joe Smith) so the single column included Joe.Smith.  Then I did a mail merge with that list to create a get that PowerShell command listed above to be individualized with each username.  And then I copied and pasted those commands into PowerShell.  Not ideal.  Ideally, you'd have a foreach command that would run though all AD users, but this is a story about what I did at this moment.  I'll update this post.

tool for checking email and DNS issues

I use lots of different tools for checking DNS and email issues. My favorite is www.dnswatch.info

But I came across a new one today which looks very helpful:

http://www.hq42.net/net_tools/index.php

There are tons of tools there - but a great one is test an email address - which even shows you a the transcript of the conversation with the remote mail server.

thoughts on attachment sizing

Email attachments cannot be of infinite size.  Different servers have different limits - but here is my general rule of thumb on attachment sizing:

Never send anything larger than 10 MB.

Only send things larger than 5 MB if you absolutely have to.

Most attachments should be 3 MB or less.

 

Large files should be sent using FTP or a service like yousendit. 

Hundreds of underliverable emails you never sent

This blog entry's goal is to give a lay person's explanation as to why a user might be receiving hundreds of delivery failures for messages that he/she never sent.

Email is insecure and very exploitable. This is a fact. The standard for email was designed in the late 60s and early 70s, long before spam and other types of abuse existed or were even thought of. Today, we live with the repercussions of the insecurity and exploitability of the original designs of the email standard. For more detail on the email standard and why it's exploitable, please see my advanced user's explanation (forthcoming as of 5/18/08).

What's happening is that an unethical spammer somewhere in the world has set up his/her own email server and is sending out spam. The exploitability of email is that this spammer can send out emails with any email address he/she wants. He can use bill.gates@microsoft.com; he can use dave@t-solve.com; he can use tom.brady@newenglandpatriots.com. The spammer can send using any address he/she wants - but the email standard does not require that the spammer be a legitimate sender of that domain. The email standard also does not require that the receiving email server check to see that an email is coming from the legitimate server for that domain.

So the spammer can send emails to anyone he/she wants with YOUR address. He/she can be doing that from his/her house in China, Norway, or next door. We have no control over this because it can be done from anywhere in the world. And this spammer is sending emails potentially with YOUR address (as well as other people's addresses) to other people. This process does not involve your server and is not disallowed in the email standard, so we have no control over it.

In these instances where a user gets several hundred undeliverable emails ... the spammer sends out spams to a random list of email addresses (many of which do not exist). And then the recipient's email server sends a bounceback to the sender's address (your email address) that says "undeliverable - this address does not exist."

So what can be done about this? Not a lot, unfortunately. The spammer is taking advantage of an exploitable part of the email standard. It may be unethical and improper, but it's not preventable.

The standard way to deal with this issue is to ignore the emails. Oftentimes, the spammer will send out 200 to 500 of theses emails over a period of 2 to 5 hours and then stop.

For additional questions on this issue, please email me:
http://www.t-solve.com/contact.html