Tag Archives: email

Posts related to email services

Hostnames for eximstats Rejections

I use eximstats to report my daily email traffic. I have a fairly high rate of rejections, and wanted hostnames listed in the rejection reports.    To resolve this I developed a patch to capture the hostname related to the IP address, and add this data to the rejection reports.

The enhanced list saves me the effort of looking up IP addresses that were repeatedly addressed.   Occasionally, these are from legitimate servers that have been misconfigured.  DNS problems are often the cause. Continue reading

Faking IMAP for Exchange Email

For years I have had problems getting IMAP access to exchange servers.  Many organizations don’t enable IMAP on their Exchange servers, and others don’t do it right.   I recently came across a solution that  works with the Microsoft WebMail interface to provide an IMAP and/or POP3 access to the mail servers.  This allows use of IMAP mail clients like Thunderbird or Microsoft Live Mail.

This article describes the solution as I have implemented it.  It uses the open source DavMail Gateway written in Java.  It accesses a WebMail server and provides access via standard protocols like IMAP, SMTP, and CalDav.   This program can be configured for personal use on a desktop, or group use on a server.  When configuring a server, it is recommended that you provide SSL keys so that secure protocols can be used. Continue reading

Detecting Email Server Forgery

Most of the spam I see has been sent by servers forging or otherwise obscuring their server identity.  RFC2505 states that the server identity and sender address are easily forged.  Of these, it is easiest to identify server forgery.  Very little, if any, of the personal email has a forged server identity.  Unfortunately, legitimate bulk and automated email often shows signs of server identity.   If you deliver either of these types of email this article will provide information of fixing the situation.

The rules here apply email originating from the Internet only.    Mail User Agents submitting email are expected to violate these rules.  MUAs should use an authenticated encrypted connection to the Submission port (576).  Relay servers should not apply these rules to connections originating form the local network. Continue reading

Securing your Email Reputation with SPF

SPF (Server Policy Framework) is a simple means to limit the ability of  others to forge your identity in email.  I first implemented it after a forged identity under my domain was used to send Spam.  Once SPF was configured,  the bounce messages quickly dropped off.

Although not as frequently implemented as sender address checks, SPF can  be used to prevent forgery of the HELO identity.  My mail server uses SPF to check the Identity of the server.  This is easier to configure and more reliable than checking the domain in the Mail from address.  Even though I treat Neutral and Softfail policies as a Fail policy, I have not detected any false negatives.   I verify both the address returned by the PTR record for the host and the address in the HELO command.  This is primarily because the PTR record is more likely to have a valid domain. Continue reading

Email Logins for Dovecot and Exim

While I was cleaning up my Ubuntu Email server configuration, I consolidated my login security.  My SMTP server is Exim and my IMAP server is Dovecot.  Mail User Agents (MUAs) use authentication over TLS encrypted connections to access IMAP and SMTP.   Both programs had their own password configuration.

Exim includes Dovecot in its supported authentication mechanisms.  This enables one authentication mechanism to be used for both SMTP and IMAP (or POP3).   This post also includes configuration details for forced authentication over the Submission port. Continue reading

Blocking Spam with Exim

Recent reports indicate that spam is increasing again.  I have been using Exim to filter spam for several years.  Some recent tuning I have done have decreased the percent of spam which reaches my spam filters.   This article provides a discussion of the techniques used, and provides implementation examples.   Spambots tend to be simple programs which don’t handle slow servers very well.   Using a greylist is effective method of blocking them as they usually don’t retry.   My latest changes use delays to cause many spambots to abandon their attempt.  Greylisting is used only for poorly configured servers that make it to the Recipient command.

Continue reading

Email Policy

SysteMajik.com actively discourages Spam and email sent from incorrectly configured servers. Legitimate email from correctly configured servers should have little problem being delivered. We believe we are relatively complaint with  RFC 2505 – Anti-Spam Recommendations for SMTP MTAs and other RFCs mentioned at the end of this document.

This article covers our  policy implementation for incoming and outgoing email.  These policies apply to all email destined to or originating from systemajik.com,  toucantango.com, and other domains for which we may handle email. Continue reading

Implementing DKIM with Exim

This article was updated in February 2014 to reflect changes policy and reporting options. The earlier ADSP (Author Domain Signing Practices) information has been removed.

DomainKeys Identified Mail (DKIM) provides a method to confirm the origin of an e-mail. DKIM also provides some protection against tampering. Unlike SPF, this validation applies to the contents of the message when it is signed. Like SPF, the information required for validation is added to DNS. Continue reading