$$lim_{s-> \infty}\phi(sz)e^{-s}$$
where $\phi$ is the series $$\sum_0^\infty \frac{a_n}{n!}(sz)^n$$ and is entire.
Also, assume that we have this upper bound: $|\phi(sz)|$ $\le$M$e^{|sz|}$.
Then, we can look at this limit instead:
$$lim_{s-> \infty}\ Me^{s(|z|-1)}$$
which is just zero for |z| < 1 easily -- but it is not zero for |z| =1 or |z|>1.
Note: s is real, while z is complex.
Thanks,