Email Marketing (check competitors?)

Is there any way to check how many subscribers another company has in their email marketing list? I'm not asking about stealing or seeing HOW people get their list, just a way to maybe even estimate how many people someone has in their list? A competitor of mine loves to boast about their huge 250,000 list that they have, but I personally think they are lying and ripping people off by charging crazy prices to advertise to their supposedly superior subscriber count.

No you can't, lists are stored on secured places and nobody can see it, at last shouldn't see it.
The only way to find out is Social Engineering, make the owner of the list tell you the truth .

hmmm alright thanks guys. Not trying to spy but I guess it may be unethical.