Question

${\mathcal{\huge{\underline{\green{RIDDLE}}}}}$

I start with 'M' and end with 'X' and have never ending amount of letters.

${\bold{\underline{What\:I\:am}}}$

_______________________

Good afternoon !!

Answer 1

I think the answer is a MAILBOX...

Answer 2

[Tex]\bold{Heya\: Mate}[/tex]

I start with 'M' and end with 'X' and have never ending amount of letters.

Answer is▶️▶️$\boxed{mailbox}$

@skb