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Filtering PDF-/XLS-/Image-Spam With ClamAV (And ISPConfig) On Debian/Ubuntu
There is currently a lot of spam where the spam "information" is attached as .pdf or .xls files, sometime also hidden inside a .zip file. While these spam mails are not easy to catch with e.g. SpamAssassin or a Bayes filter, the ClamAV virus scanner can catch them easily when it is fed with the correct signatures as ClamAV is built to scan mail attachments.
How to Avoid Being Blacklisted
A blacklist usually refers to a list of e-mail or IP addresses known to send spam e-mails or some other type of unsolicited messages. Such lists are currently used by mail servers for filtering incoming e-mails and blocking the ones listed, in order to improve mail security and integrity. The blacklist is also the opposite of what is called a whitelist.
Postfix Monitoring With Mailgraph And pflogsumm On Debian Etch
This article describes how you can monitor your Postfix mailserver with the tools Mailgraph and pflogsumm. Mailgraph creates daily, weekly, monthly, and yearly graphs of sent, received, bounced, and rejected emails and also of spam and viruses, if SpamAssassin and ClamAV are integrated into Postfix (e.g. using amavisd-new). These graphs can be accessed with a browser, whereas pflogsumm ("Postfix Log Entry Summarizer") can be used to send reports of Postfix activity per email.
Setting Up Postfix As A Backup MX
In this tutorial I will show how you can set up a Postfix mailserver as a backup mail exchanger for a domain so that it accepts mails for this domain in case the primary mail exchanger is down or unreachable, and passes the mails on to the primary MX once that one is up again.
Retrieving Emails From Remote Servers With getmail (Debian Etch)
Getmail is a program for retrieving emails from remote servers; it is very similar to fetchmail, but more flexible. For example, it can be configured to deliver mails directly to a Maildir or mbox mailbox without the need for an MTA such as Postfix, but of course it can also pipe the mails through an MTA if you want. Getmail can use so called filters such as SpamAssassin and ClamAV to scan the mails, and you can even tell getmail to delete mails on the original server only after a certain number of days.
Converting All Your MS Outlook PST Files To Maildir Format
One of the challenges you may face when converting an office from Microsoft Windows to Linux is that many people archive their e-mail in PST files. There are PST tools available, but most of them are commercial, since the PST file format is closed and protected by Microsoft. There are several non-commercial methods to achieve roughly the same goal, and in this tutorial we use IMAP (more specifically, courier-imap) to convert all our e-mails from PST to the Maildir format. The advantage of this approach is that you also lay the foundation for a new mail system, with all your old e-mails already imported the day you switch over.
Introduction to Antispam Practices
Competitive Antispam products, proper legislation, efforts towards a better user education, it has all been tried in order to stop spam. However, unsolicited emails keep consuming the space and time of all email users. Moreover, spam messages can be the cause of serious virus and spyware outbreaks, while others “phish” for sensitive information like bank accounts and passwords.
Virtual Users And Domains With Postfix, Courier And MySQL (Debian Etch)
This document describes how to install a mail server based on Postfix that is based on virtual users and domains, i.e. users and domains that are in a MySQL database. I'll also demonstrate the installation and configuration of Courier (Courier-POP3, Courier-IMAP), so that Courier can authenticate against the same MySQL database Postfix uses.
How To Block Spam Before It Enters The Server (Postfix)
The last few weeks have seen a dramatic increase in spam (once again). Estimates say that spam makes now up for 80 - 90% of all emails, and many mail servers have difficulties in managing the additional load caused by the latest spam, and spam filters such as SpamAssassin do not recognize large parts of that spam as they did before. Fortunately, we can block a big amount of that spam at the MTA level, for example by using blacklists, running tests on the sender and recipient domains, etc. An additional benefit of doing this is that it lowers the load on the mail servers because the (resource-hungry) spamfilters have to look at less emails.
Retrieving Emails From Remote Servers With fetchmail (Debian Etch)
Fetchmail is a program for retrieving emails from remote servers. Imagine you have five email accounts on five different servers. Of course, you don't want to connect to each of them to get your emails. This is where fetchmail comes into play. If you have a user account on a Linux server, you can make fetchmail download emails from remote servers and put them into just one mailbox (the one of your Linux user), from where you can retrieve them with your email client (e.g. Thunderbird or Outlook).