Part 1: default font
Row A has no font set anywhere. Compare its letter shapes with the named fonts below it.
A. No font setRag Quick gy 0123 Wl1I
B. ArialRag Quick gy 0123 Wl1I
C. HelveticaRag Quick gy 0123 Wl1I
D. Times New RomanRag Quick gy 0123 Wl1I
E. CalibriRag Quick gy 0123 Wl1I
F. AptosRag Quick gy 0123 Wl1I
G. Segoe UIRag Quick gy 0123 Wl1I
H. RobotoRag Quick gy 0123 Wl1I
I. System UIRag Quick gy 0123 Wl1I
J. GeorgiaRag Quick gy 0123 Wl1I
Part 2: background images
Red means the background image did not show. A pattern of logos means it did.
1. Inline background-image 
2. Inline background shorthand 
3. Background image in a style block 
4. background attribute 
5. VML for classic Outlook
VML row
End of test. MailSlurp email client support report, v1.