With all the movement with DomainKeys and the updated DomainKeys Identified Mail (better known as DKIM), much has changed in the “standards” and it is difficult gathering the correct steps to do when integrating with sendmail on Fedora.

Following these simple steps, you should be able to get it configured and running with little headache. Note there are a lot of moving pieces and a misstep on one will cause failure. Check and re-check each step before moving on.

1. Install the DKIM package using yum
2. Generate the public and private keys
3. Create the DNS records
   1. Public DomainKey Selector
   2. Author Domain Signing Practices
4. Modify the configuration files
   1. Private keys
   2. Milter configuration
   3. KeyList
   4. Internal hosts
5. Start the dkim-milter service
6. Integrate with sendmail
7. Test
8. Caveats

(more…)

If you establish a Facebook page for a business and have emails that are regularly sent out, you can add more value to the email by ensuring the sender’s email address is linked to the Facebook account and the postings are public. If set up correctly, anyone using Outlook Social Connector for Facebook will see content related to the company (the page’s wall posts) with every email. This is an easy way to push out more information and entice someone to visit your Facebook page.

Of course this applies to all other Social Connectors and new ones as they are developed.

I have front-ended my Exchange Server 2010 with sendmail, preferring to use Linux utilities such as SpamAssassin and Clam AV to filter out the bad stuff before sending it to my email server. I also create generic email addresses that I use to give out. Recently, I was having a difficult time sending an email to a newly created email address with a domain that is served by my Exchange Server. In Outlook 2010, after inputting an email address such as special-email@epicminds.com, Outlook would display “this e-mail message cannot be delivered to special-email@epicminds.com because the e-mail address is no longer valid”.

The resolution for this issue cannot be found in Google – no hits are found for the exact error message. It occurred to me that since the Exchange server was responsible for the domain, it was determining the email address was invalid, and this is indeed the case. The solution is simple: change the Type for the Accepted Domain in the Hub Transport from Authoritative to Internal Relay.

To recap:

1. Start Exchange Management Console
2. In the console tree under the Exchange Server select Hub Transport under Organization Configuration
3. Select the Accepted Domains tab
4. Right-click on the accepted domain and select Properties
5. Change the Type to Internal Relay Domain
6. Click Apply

This will enable the Outlook client to accept an email address using that accepted domain that does not have a mailbox tied to the address.

I frequently give out email addresses using <yourdomain@mydomain.com>; this way I am able to track the source of spam I receive. It also easily enables me to reject future email to that account by adding a line to sendmail‘s access file along with a “pleasant” 550 response message when warranted. My problem has been how to send an e-mail using that address.

The solution is quite simple – I specify the address in the Reply-To field of my e-mail client and use MIMEDefang to add an action to change the From: Header to the Reply-To: header.

Fortunately, I already had MIMEDefang added into the mix as I use it and SpamAssassin for processing mail. I had some difficulty understanding where and how to add the logic in the mimedefang-filter perl script but finally found useful information at http://www.mickeyhill.com/mimedefang-howto/ and through searching archives of the MIMEDefang mailing list.

I don’t have any users that use Reply-To and so the determination of when to apply this is quite simple; if the mail originated on the local LAN and the Reply-To header exists and has an email address then change the From header to the Reply-To contents and delete the Reply-To header. You may need to alter the contents of the if logic.

This is accomplished with the following code, placed near the end of sub filter_end:

    # Rewrite From: header with Reply-To: if it exists
    if ($RelayAddr =~ "^192\.168\.1\." && $entity->head->get('Reply-To') =~ /@/) {
        action_change_header('From', $entity->head->get('Reply-To'));
        action_delete_header('Reply-To');
    }