Growth of entire functions represented by Dirichlet series

Let, $\displaystyle F(z)=\sum _{n=1}^\infty a_ne^{\lambda _nz}$ be an entire function represented in the whole of the plane by an absolutely convergent Dirichlet series such that
$$0\leqslant \lambda _1<\lambda _2<\dotsb ,\qquad \varlimsup _{n\to \infty }\frac {\ln n}{\lambda _n}=\mu \in [0,+\infty ).$$
The connection between the growth of the quantity
$$M(F;x)=\sup \bigl \{|F(x+iy)|:|y|<+\infty \bigr \},\qquad x\to +\infty.$$
End the behaviour of $|a_n|$ and $\lambda_n$ as $n\to \infty$ is described in general form.