I just designed an email campaign for a client and, naturally, I created the templates in multi-part MIME format. One major concern, especially since this is a B to B company, is that many readers will have their images turned off in their email readers. My client was extremely concerned that his logo would not display and his readers would not know where the email message came from.
  
(I didn't necessarily agree with this. Relevant, well written content should speak for itself. But I decided to give my client what he wanted…)
 
I didn't want to abandon the html version altogether because my client is in a very graphically-based industry. So, here’s the workaround I designed - that you can easily tweak for your own email template.
  

Here is a low resolution version of the original logo

David Noble
Productions

And here is the text-based logo

Now granted, some logos are a little harder to "textualize" than others (can I trademark that term?). You may need to play around with yours awhile, or even higher a graphic designer to create a text-only version. Here are a few tips to keep in mind:

• Use "ordinary" fonts to guarantee the best display. You never know what fonts will be installed on your readers' machines. Your log will appear differently across different platforms.  
   
• Designate a font family rather than just a single font.  For instance, in the logo above, you may be seeing the text "David Noble" in Apple Chancery, Comic Sans MS, Skia,  or another Fantasy font, depending on what fonts you have installed on your computer. 
   
• Don't go too large with the font, as this can trigger spam filters. 
   
• Reverse type can be difficult to read on a computer monitor. If your audience is older or if there are any vision concerns, avoid reverse type. 
   
• It's not necessary to rebrand your entire organization. An email-only logo certainly won't cause your customers to drop off like flies. We continue to use David's original logo in all his other marketing pieces. 
   
• The rendition of spacer images can be quirky across email clients. (I used a spacer image to display the thin blue border around the top and bottom of the logo.) However, this is still a more reliable method than using CSS.

I did use the film graphic in the second table cell. This, obviously, won't display for any readers who have their images turned off. But they'll still see the important logo information, i.e. the name.
 
Using a popular font and specifying a font family is critical to the creation of your textualized logo. You can grab a free, downloadable version of the forty most popular fonts at my website.
  
  
Time to implement: It's hard to say how long it will take to textualize your logo. It really depends on how creative you want to be. Something as simple as matching a similar font and similar color can take less than 10 minutes. Creating a cross-platform, table-based layout with several fonts and several colors that will be easily implemented into your email template can take up to two hours.