  Multi-loop Feynman integrals are key objects for the high-order correction
computations in high energy phenomenology. These integrals with multiple
scales, may have complicated symbol structures. We show that the dual conformal
symmetry sheds light on the alphabet and symbol structures of multi-loop
Feynman integrals. In this paper, first, as a cutting-edge example, we derive
the two-loop four-external-mass Feynman integrals with uniform transcendental
(UT) weights, based on the latest developments on UT integrals. Then we show
that all the symbol letters can be nicely obtained from those of
closely-related dual conformal integrals, by sending a dual point to infinity.
Certain properties of the symbol such as first two entries and extended
Steinmann relations are also studied from analogous properties of dual
conformal integrals.
