How to use CalDAV with Thunderbird and Lightning

CalDAV is another method that can be used to synchronize your mail server calendar with an email client calendar. Any CalDAV enabled calendar should provide this functionality. Thunderbird and Lightning (Calendar add-on) do provide support for CalDAV. In this post I'm going to provide details of how to configure Thunderbird/Lightning to sync with your CalDAV server.

1. Prerequisites
2. Setup network calendar
3. Sync Calendar

Prerequisites - Before getting started you need the following:

Update: Only applies to Thunderbird 2.x. Version 3.x does not yet support Lightning.

• Thunderbird (Version 2.x ONLY)
• Lightning add-on. Check with your mail server developer for compatibility.
• Mail server IP address or host name.
• CalDAV shared name or calendar name.
• The CalDAV username and password. Usually this is the same as your email account login.

Setup network calendar - After you have successfully configured an email account in Thunderbird and installed the Lightning Add-on you are ready to add your CalDAV network calendar.

Right Click under Home calendar and select New Calendar.

At this screen select 'On the Network' and press Next.

In this screen you need to select CalDAV as Format. In the Location field enter your mail servers CalDAV URL. The URL entered in this field can vary by mail server or CalDAV server. Please refer to your mail server requirements for proper URL structure. Here's two examples from VisNetic MailServer and Kerio MailServer.

Update: IceWarp Mail Server
http://[server]:[port]/webdav/[account]/[folder]/
http://192.168.1.2/webdav/user@your_domain/Events/

192.168.1.2 = the IP of VisNetic MailServer
Port = default port for VisNetic MailServer Web Control
user@your_domain = your email address
Events = this is the default name for your calendar in VisNetic MailServer

Kerio MailServer
http://[server]/calendars/[domain]/[shared calendar user]/[calendar name]
http://192.168.1.2/calendars/your_domain/user/calendar

After pressing Next to the URL window you will be asked to name the calendar and select the email account associated with this calendar. Select Next and Finish.

Sync Calendar - The calendar should ask for your username and password, usually this is your email address and password. After successful authentication the calendar on your mail server will reside in Lightning. If you add a calendar event in Lightning it will be sync'd to your mail server and the same applies to your mail server (usually via Webmail) calendar.

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Use NSLOOKUP to Find PTR or rDNS record.

Nslookup has some very useful tools that can make quick work of DNS lookups. In this article I'm going to show how to use nslookup to find PTR or rDNS records.

Since rDNS or PTR lookups are based on reversing the IP and performing a PTR lookup you may need to first find the IP address for a given MX record and perform the PTR lookup on that IP. If you know what IP you want to perform the lookup on you can skip right to PTR lookup. In our example I'm going to find the PTR record for an IP from Yahoo mail.

1. Open nslookup and enter help.
2. Set nslookup to type MX and lookup MX for Yahoo.com.
   
3. Find IP for one of Yahoo's MX records.
4. Set nslookup to PTR and lookup IP.
5. Show result when no PTR exist.

Open nslookup - help.

From a command prompt type nslookup and then help. Review the available options.


Set nslookup to type MX and lookup MX for Yahoo.com.

Type 'set type=mx' and enter, then type 'yahoo.com', without the single quotes.

Notice that several MX records are returned for yahoo.com. For this example I'm going to use 'c.mx.mail.yahoo.com', however, you can lookup any one of the IP's to find PTR records. Look for the MX record internet address 216.39.53.3.

Set nslookup to PTR and lookup IP.

Type 'set type=ptr' and enter, then type 216.39.53.3 and enter. You will receive a response to the PTR lookup if one exist. If not, the response will say no record exist.

The results returned shows the IP was sent in the reverse order and that IP does have a PTR record. The PTR record almost always has a name associated with it as shown below.

3.53.39.216.in-addr.arpa name = mta-v14.mail.vip.re4.yahoo.com

Show result when no PTR exist.

Type 1.2.3.4 and you will see a PTR lookup that does not exist for that IP.

> 1.2.3.4
Server: resolver.qwest.net
Address: 205.171.2.65

*** resolver.qwest.net can't find 4.3.2.1.in-addr.arpa.: Non-existent domain

What is SPF (Sender Policy Framework)?

Sender Policy Framework (SPF) is an antispam measure designed to fight email address forgery. Using SPF, the Internet domain of an email sender can be authenticated for that sender, thereby discouraging spammers who routinely disguise the origin of their email--a practice known as email spoofing. Under this practice, spammers forge the email header so that the message appears to have originated from someone or somewhere else. Spammers often use spoofing in an attempt to get recipients to open, and possibly even respond to, their solicitations.

To combat email spoofing organizations are publishing SPF records for their own domains and then using SPF to distinguish forgeries from real email sent by other domains. Published SPF records include attributes that uniquely describe an organization's email, including authorized senders and mail server IP addresses. On the receiving end, organizations using SPF verify the authenticity of each sender's FROM email address by performing DNS queries (accessing the published SPF record) to confirm that the sending server is authorized to send mail on behalf of that address.

Most mail servers use SPF with SpamAssassin and use a scoring system to validate whether the message is likely spam, for example,

When the Sender SPF record passes, a negative spam score can be recorded to reduce the possibility of the message being marked as spam.

When the Sender SPF record fails, the spam score can be increased by 5 points to insure it's marked as spam.

When unable to verify an SPF record (soft-fail), the spam score can be increased slightly.

Additional information on how to configure SPF can be found at Open SPF:

http://www.openspf.org/