"Ten list został napisany przez mężczyznę."

Translation: This letter was written by a man.

[HarveyPenf1]

would "był" work here too, instead of został? if not, whats the difference?

[Shamarth]

You need to use 'został' with perfective verbs and 'był' with imperfective verbs.

[Jellei]

Actually, "był" works. It seems worse to me, I can't say why, but it works.

[alik1989]

Would napisany mężczyzną be also correct? If so, what would be the difference in meaning?

[immery]

no, no no nononononono

I will not try to imagine how you can write using a man. (instead of a pen).

[Zimowski]

it's a good idea for a horror film about some furious giants

[Euhan1]

Writing in the snow...

[Zimowski]

As I understand it, you can't avoid using "przez" if someone who does the action is a living creature.

So you can say: List został uniesiony wiatrem. And: List został uniesiony przez wiatr

But: List został napisany przez mężczyznę.

More about it here: http://sjp.pwn.pl/poradnia/haslo/miotany-falami;12502.html . There's a good example from Bible: Łódź zaś była miotana falami

[Ten_Pies_I_Brew]

Is there any reason a Polish speaker would say "Ten list został napisany przez mężczyznę" instead of just "Ten list napisał mężczyzna"?

[Jellei]

We're just practicing passive voice here, your second sentence sounds more likely in reality.

And I think it can be an accepted answer here. Maybe it's not passive voice, but the word order makes me think that "was written by a man" is a likely English translation. Added.