All posts by jaapwesselius

PowerShell

Resolve-DnsName PowerShell command

Leave a comment

Every now and then you find these small little things that turn out to be very useful. The Resolve-DnsName cmdlet in PowerShell is such a brilliant thing, and it is a nice replacement for NSLOOKUP. Since it is a PowerShell cmdlet you can easily use it in scripts. It looks like this command was introduced in Windows Server 2012 R2, but I found out only a couple of days ago.

As an Exchange consultant I can use the Resolve-DnsName for retrieving my MX records, or my DMARC record:

image

Using the Get-Help Resolve-DnsName command you can get more information, if you need some examples on how to use it you can use the -Examples option, or the -Detailed and -Full options.

image

Very useful for an Exchange admin, and it can be used in PowerShell scripts.

Exchange

ITDev Connections 2016 Las Vegas

1 Comment

image.png

From October 10 until October 13 the annual IT/Dev Connection was held in the Aria Resort and Casino in Las Vegas, for the 15th time this year.

IT/Dev Connection is a relatively small tech conference with approx. 1000 ~ 1250 attendees (my guess). Because of this size the event is very accessible, attendees can approach speakers, vendors and sponsors easily without being too crowded. It happens regularly that a speaker is walking through the hallway or having lunch at the venue, and it being approached by attendees, this makes an event like this much fun, both for speakers as well as attendees.

The event has a strong Microsoft technology focus although you can see some other sessions as well like sessions about Docker or Amazon Web Services for example. The good thing about this event is that it is an event about Microsoft technology, not organized by Microsoft and sessions are presented by non-Microsoft employees so you get plenty of real world scenarios instead of the marketing talk you typically get at Ignite. Even better, this year there weren’t even keynote sessions since they contain too much marketing blahblah J

Continue reading ITDev Connections 2016 Las Vegas →

PowerShell

Rename filenames containing strange characters with PowerShell

Leave a comment

Recently I had a computer with tons of file on it which I had to backup and upload to OneDrive for Business (OdfB). For some unknown reason there were lots of file that had the HTML representation of a space character in it (%20), there were also filenames containing a # character.

Needless to say, the OdfB client didn’t like it, and kept complaining about not being able to upload files, it wanted to try again and again…. Renaming these files (in hundreds of directories) was not something I fancied, but this is great for PowerShell to figure out.

To find all files that contained the %20 in it I used the following command: 

Dir -Recurse | Where-Object {$_.Name -like "*%20*" }

image

Now it’s just a matter of renaming the “%20” with another character, for example an underscore character “_”, like this: 

Dir -Recurse | Where-Object {$_.Name -like "*%20*" } | Rename-Item -NewName { $_.Name -replace "%20","_" }

Et voila, all “%20” characters are now removed from the filenames, and ready to be uploaded to OneDrive for Business

image

Exchange

SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part III

4 Comments

In the previous two blog posts I have discussed SPF and DKIM as a way of validating the authenticity of email messages. SPF is using an SPF record in public DNS where all legitimate outbound SMTP servers for a domain are listed. A receiving SMTP server can check this DNS record to make sure the sending mail server is allowed to send email messages on behalf of the user or his organization.

DKIM is about signing and verifying header information in email messages. A sending mail server can digitally sign messages, using a private key that’s only available to the sending mail server. The receiving mail server checks the public key in DNS to verify the signed information in the email message. Since the private key is only available to the sending organization’s mail servers, the receiving mail server knows that it’s a legitimate mail server, and thus a legitimate email message.

As a reminder, my test environment is configured as follows:

image

There’s an Exchange 2016 CU2 Mailbox server hosting several Mailboxes, and there’s an Exchange 2016 CU2 Edge Transport server. Using Edge Synchronization all inbound and outbound SMTP traffic is handled by the Edge Transport server.

In the previous two blog posts an SPF record was created and implemented, and DKIM including a DKIM signing module on the Edge Transport server was implemented and functioning correctly.

This last blog in a series of three discusses DMARC, which is built on top of SPF and DKIM. Continue reading SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part III →

Exchange

SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part II

2 Comments

In the previous blogpost I have been discussing how SPF works and how it uses public DNS to validate the authenticity of the sending SMTP servers. When SPF is implemented correctly a receiving mail server can validate is the sending mail server is allowed to send email on behalf of the sender or his organization.

In this blogpost I will discuss DKIM signing as an additional (and more complicated, and more difficult to spoof) step in email validation.

As a quick reminder, here’s how my lab environment looks like:

image

There’s an Exchange 2016 CU2 Mailbox server hosting several Mailboxes, and there’s an Exchange 2016 CU2 Edge Transport server. An Edge synchronization will make sure that all inbound and outbound SMTP traffic is handled by the Edge Transport server.

In my previous blogpost an SPF record was created and implemented with the following value:

v=spf1 a:smtphost.exchangelabs.nl ~all

so receiving mail servers can validate that my Edge Transport server is allowed to send email on my behalf, and when mail is originating from another mail server it might well be a spoofed message.

But for now let’s continue with DKIM. Continue reading SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part II →