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A Debian Developer's observations

20th September 2011 12:10 (GMT)
TNEF or how to lock-up your e-mails

As the administrator for several MTAs I've received my fair share of support requests for "unreadable" e-mails. They generally have an attachment called winmail.dat. This is what all (for exceptions see the rest of this blog post) non-Outlook MUAs can display, when they receive an e-mail with the application/ms-tnef (or application/vnd.ms-tnef) MIME type. TNEF is a propietary format cooked up in Redmond. When chosen, the e-mail in question isn't sent as text/plain or at least text/html, but the entire e-mail is put into an TNEF-encoded attachment, most often called winmail.dat, in which you (most commonly) find the content of the e-mail in RTF, possible attachments are also put into the winmail.dat.

The easieast solution for all involved parties is to convince the sender, that her Outlook and/or Exchange setup needs fixing (disabling TNEF in Outlook and Exchange 2003). Sadly this won't work all the time. The other solutions are to either filter the e-mails on your e-mail server and run them through something like ytnef_smtpd.py (please note, that this might be legally problematic for you as a service provider, opening an e-mail, even automatically, is a violation of communication privacy rights in many jurisdictions). Or, if the legal problem is too big or can't be solved through an local server installation (e.g. because there is no server running 24/7), you're left with either using Outlook (probably what Microsoft intended) or you can use a plug-in/add-on for your client. I've tested the LookOut add-on for icedove and it seems to work well. There are of course plug-ins for many other clients, but I can't honestly tell whether they work or not.

[UPDATE 2011-09-20]: Fellow Debian Developer Josselin Mouette wrote me, that Evolution is capable of reading TNEF-encoded e-mails out of the box, but he also said that [TNEF e-mails should] be banned by all means.[/UPDATE 2011-09-20]

Now, before I close, please always try to convince the sender/postmaster to fix their setup. It has only advantages: text/plain e-mails are smaller, they're less likely to contain malicious code (i.e. no parts hidden away from the virus scanner on the mail server (amavis can read TNEF e-mails, if libconvert-tnef-perl is installed)) and all recipients can open the e-mails with the client of their choice.

Permalink | debian, proprietary-formats.
28th October 2011 19:16 (GMT)
Google recommends using OpenStreetMaps/OpenLayers

Maybe you've already heard, that Google is starting to charge a fee for using the Maps API (Google may decide you're an non-profit organization and waive the fees). That is, in my opinion, Google telling you to look for better alternatives. And thanks to the awesome effort of the OpenStreetMaps community, there is such an alternative.

Thus today's addition to the mini-tips series will tell you, how you get an OpenStreetMaps-powered map on your website.

  1. First you need to determine the coordinates, where you want to center, the map. You can do this with OpenRouteService.org. Just search for the address, right-click on the marker highlighting the result, and set it as e.g. your start point, that'll give you the coordinates in the start field on the left. Alternatively you can just move your pointer over a place on the map and have a look at the lower right corner, where the current coordinates for the pointer position are displayed.
  2. Then you need to add a few things to the website, where the card is to be shown:
    • Include the OpenLayers script in the <head> of your webpage:

      <script src="http://www.openlayers.org/api/OpenLayers.js" type="text/javascript" />
    • Add a short ECMAScript snippet right after that, which will initialize your map:

      function osmInit() {
        document.getElementById("ol_map").style.display = 'block';
        var lonLat = new OpenLayers.LonLat(13.376096, 52.518598) // Center of the map
          new OpenLayers.Projection("EPSG:4326"),   // transform from WGS 1984
          new OpenLayers.Projection("EPSG:900913")  // to Spherical Mercator Projection
        var map = new OpenLayers.Map("ol_map");
        var osmlayer = new OpenLayers.Layer.OSM();
          16 // Zoom level

      The first line is not needed, but I find it nice to hide the map on default, in case the user has disabled ECMAScript they haven't a large empty area somewhere on the website. The first line changes then the display value from "none" to "block". The rest is, I hope, already explained by the code itself.

    • Now only two more changes are needed, first you need to add onload="osmInit();" to your <body> tag. And afterwards an element (say a <p>) with the ID ol_map somewhere in the website <body>. You should set a width and height for that tag (style is your friend), otherwise the map might be bigger than you like.
  3. Done. Enjoy your free (not just as in free beer) map!

You can, of course, customize your map further by adding additional layers and changing the available options (e.g. the zoom level). If you would want to mark a location on your map, you'd need to add something like

var markers = new OpenLayers.Layer.Markers("POI1");
markers.addMarker(new OpenLayers.Marker(lonLat));

to your ECMAScript snipped after you added the OpenStreetMaps layer. These three lines would mark the location given by the variable lonLat.

For further information, you can check out the OpenStreetMaps wiki and the OpenLayers documentation.

In case you wonder, where my coordinates from this example point, you can check. Oh, and don't forget to consider a donation to OpenStreetMaps, so the project can pay the bills for its servers.

Permalink | cheat-sheet, debian, proprietary-formats, xhtml.

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