I have to send planned support notification emails on system events (service window, alerts, etc). I see that most of such emails I receive from my vendors are in plain text format.
I wonder should I to stick to plain text format as well (with accompanied limitations) or provide HTML based one with better visualization?
I am aware of limited HTML rendering capabilities of different email clients, but I suppose that not complex HTML with images will be OK.
The decision should start with if you will possibly have any clients that will not accept HTML email.
This is less common that it once was, but you still may have some security concious users that don't allow HTML.
However you can provide a plain text alternative, within the same email.
http://www.wilsonweb.com/wmt5/html-email-multi.htm
Also you should consider does the HTML provide value above the plain text? For me the information I usually receive is transmitted within the subject line for maximum readability.