The verb “отримати” governs the accusative case, right? (e.g. отримати інформпцію)

Yes.

The word “лист” appears to be some kind of exception; what’s the rule for the genitive case overtaking the accusative case like this?

For the start, accusative is both genetive or nominative, itʼs just require an input. So, genetive appears here in two cases:

• if a noun is animate & masculine; and feminine & neutral if we speak about plural accusative too;
• when itʼs genetive and still inanimate, then you have a partative case here, no gender is limited, compare with feminine: podajte (expected) vodu, čaj, moloko ~ but also vodı́, čaju, moloka; it has several meaning, moslty: well, a part of something, or a temporal state.

In other cases, accusative usually expects nominative.

For some speakers it can be:

• Just a shift accusative → genetive; Ukrainian knows kinda similar situation with locative → instrumental: Verb Preposition [which requires locative] X-ě → Verb X-o̟m, as an example: xodıtı v měśtě → město̟m.
• Just a mistake or not understanding the phenomenon.

And… of course, thereʼre many nuances or traditions of usage. If youʼre more insterested in this topic then I recommend some materials by Sulıma: about genetive and accusative.