We recommend thorough testing in a range of email programs and web mail sites. Generally, the top four below cover a high percentage of most mailing lists though bear in mind a B2B list will likely have a lower percentage of Hotmail users than a B2C one for example.

Top email clients for testing on:

1. Outlook 2003 / Outlook Express (use same rendering engine)
2. Hotmail / Windows Live Mail
3. Google GMail
4. Thunderbird
5. Yahoo! Mail
6. Outlook 2007
7. Roundcube web mail
8. AOL web mail
9. Tiscali web mail