After you've finally figured out how to design and code your first HTML email template (and, of course, your plain-text alternative version as well), don't just plop in your content and start sending campaigns to your list. You need to test your template first. Make sure it'll work in all the different email applications out there. Once you've found all the little bugs, and your template is "rock solid," you can start sending.

If you're a web designer, you're probably used to testing web pages in a few different browsers, like Internet Explorer, Mozilla Firefox, and Mac's Safari. And you're probably familiar with a few annoying inconsistencies between all the browsers, and you have a couple hacks to make things look right. Multiply all that by ten, for email design. There are tons of email applications out there that you need to test on, and they all render HTML email in their own annoying ways. Do you need to test every single newsletter across every single application, every single time you send? Of course not. Just setup a good, simple, rock solid template and test it as much as possible. Then all you do is swap out content. Here are some tips for testing your email designs...

Testing in Different Email Applications

In the past, the only way to test your campaigns was to setup a bunch of accounts at all the major ISPs, setup some test computers with different operating systems and email programs, and send test campaigns to them. It would take hours to do all this, and it really took all the fun out of email marketing. That's why we created our Inbox Inspector tool. You build your campaign, and click one button. We'll generate screenshots of how your campaign will look in every major email program, and we'll tell you if any of the major spam filters and email firewalls will block your message, and why. We'll point out what content you need to fix in order to not get blocked. We'll even check for typos and HTML coding errors.

If you prefer to test your campaigns yourself, here are some email applications you should install, and what to look for:

AOL

AOL takes spam very seriously and their free CDs are everywhere. So check to make sure your emails don't get filtered. Also, notice their "Report Spam" button. You've got to make sure your emails look relevant, or people will click that button (even if they opted in to your list!). At the time of this writing, AOL 9 has an extremely tiny "preview" pane. It's about 194 pixels wide, so make sure that your branding shows up okay under those circumstances. If your email is too wide, and your logo is right-aligned, your recipients will never see it, and they may never realize who sent it.

Apple Mail

This is Apple's free email application. You get a nice big preview pane here, and they don't do much image blocking at all (yet). Images seem to be blocked only if an email ends up in its junk folder. Apple Mail comes with its own spam filtering system that "learns" so you should test your emails for any deliverability issues.

Apple's Entourage

Kind of like Microsoft Outlook, but for the Mac (it comes with Mac Office). Their HTML email support is fine, but we noticed in earlier versions of Entourage, if you send an email in HTML format, but it consists of nothing but text and hyperlinks (no graphics or tables), then the links actually display their URL next to them. Kind of odd. But if the email actually contains a graphic or table, then the links work as coded. The issue seems to be fixed in the latest version of Entourage 2004.

Microsoft Outlook 2003

Outlook 2003 has better spam protection, so watch whether or not your emails get filtered. Also, this one's got 3 vertical panes, so your emails have less room in the preview area (see below). Three vertical panes in Outlook 2003 leave little room: Make sure you fit!

Microsoft Outlook 2000

There are lots of business users who haven't upgraded to Outlook 2003 yet. This version of Outlook predates all the vicious worms, spam, and viruses that we're used to now, so more of your emails with flash and videos and crazy stuff will actually work here. Don't let it build your confidence. That fancy stuff won't work in other programs.

Microsoft Outlook Express

This is the free version of Microsoft Outlook, installed on all Windows machines. Used mostly by "at home" recipients. Not really many HTML email issues, besides the usual "block images by default" feature that's on just about every email application these days.

Microsoft Outlook 2007

For Outlook 2007, the big change is that Microsoft is switching from using Internet Explorer (a web browser) to render HTML email to using Microsoft Word (a text editor) to render HTML email. Obviously, HTML email would render a lot better in a browser than Microsoft Word, so this is kind of a bummer. Microsoft says they're doing this because they want their customers to have more control over editing HTML email. Whatever.

Here's what you need to know about Outlook 2007:

• Background images won't work.
• Most CSS won't work.
• Flash definitely won't work.
• No forms
• No animated Gifs

Lotus Notes 6.5.3 and 6.5.4

If lots of your recipients work at very large companies, you'll need to check your emails in Lotus Notes. This is probably the most frustrating email application out there. It does the strangest things. You'll need to keep your layouts very simple. Even still, Lotus will find a way to mess things up. I'm still baffled about how they managed to make a cell in my table blink red. There are even big differences between Lotus Notes 6.5.3, vs. 6.5.4.

Eudora 6.2

Eudora has good, predictable HTML email support. We don't see too many issues to talk about here.

Mozilla Thunderbird

A free email application that's gaining in popularity. Does some odd things with alt-text, and image blocking but for the most part supports HTML email great. Thunderbird 1.5 has a feature that tries to detect "scams," where they look for hyperlinks that claim to point to a website, but the code actually links you somewhere else. If it detects a potential "scam," you get a warning across the top of the message, saying "Thunderbird thinks this message is a scam." You can click the "Not a scam" button if it was a false alarm. It's a nice idea, but it seems to give lots of false positives, especially when you use click tracking in your emails (all your links will point to a redirect script, in order to track clicks). In the Thunderbird support forums, they say that the feature is still kind of new, and they're working on refining it. We don't think it's much of a problem, as long as your emails look nice and professional.

Testing Browser-based Email Services

You might want to setup accounts with all the browser-based email services. They're usually free, so it's easy to setup lots of test accounts. You especially want to look at how browser based email services alter your HTML and CSS. Also, since these services are used by bazillions of people, their anti-spam filters are set really high. We listed them below in order of most-to-least popularity.

When you setup your test accounts with these services, leave their "junk mail filter" settings to "default." It really pays to test on these accounts before sending your campaign...

Yahoo!Mail

Pretty aggressive anti-spam filters (understandably). Other than that, they do the typical browser-based email stuff, like stripping your BODY and HEAD tags.

Yahoo!Mail Beta

A much richer browser interface, with a preview pane. So far, support for HTML email looks great.

Hotmail

Similar issues as Yahoo!Mail, where BODY and HEAD tags are stripped, so background colors and embedded CSS are lost. At one time, Hotmail was "expiring" hyperlinks in emails that were open for 5 minutes or longer.

Gmail

Extremely aggressive spam filters. And very, very little CSS support. It strips embedded CSS, (even if you keep the CSS out of the < > tag). It also strips every "class" code that it finds (such as in < >). To get CSS to work in Gmail, you'll need to use inline styles. Otherwise, your fonts will default to Arial, colored black, and about 13 pixels in size. If your fonts don't adhere to your CSS rules, check to see if they end up blowing out your tables cells, or wrapping in weird ways.

Check Different ISPs, too

If possible, check your emails when they're sent through different ISPs. Different email servers will alter your messages before they even get to the recipient's email application. For instance, some ISPs use email servers that will strip any content below a line in your email that starts with a period (I know, weird, huh?). We've been surprised at how differently email looks when checked in Outlook 2003, but received through:

• Comcast
• Bellsouth
• Earthlink

Send tests to friends and co-workers

If you can't setup a few test computers, keep your designs really simple, and send each campaign to a few friends or office-mates. Just ask them to let you know if anything looks "off" or broken to them.