Learn Hardcore Finnish: Tänään tulostusjono on täynnä, joten lähetän tiedoston sähköpostitse. - Today the print queue is full, so I will send the file by email.

Finnish often drops personal pronouns because the verb ending already shows the person.
lähetän = I send / I will send (1st person singular).
You can add minä for emphasis or contrast: Minä lähetän tiedoston… (implying “I (not someone else) will send…”).

What does tänään do, and can it appear somewhere else in the sentence?

tänään means today and works as a time adverb. Finnish is flexible with adverb placement; the beginning is common when you want to set the time/topic first. For example:

Tänään tulostusjono on täynnä… (Today, the print queue is full…)
Tulostusjono on tänään täynnä… (The print queue is full today…)

Both are correct; the difference is mostly what you foreground.

What is tulostusjono exactly? Is it one word or two?

It’s a compound noun written as one word:

tulostus = printing / printout (related to tulostaa, “to print”)
jono = queue / line
So tulostusjono = print queue.

Finnish compounds are extremely common and are usually written as a single word.

Why does it say on täynnä instead of something like on täysi?

Both can mean “is full,” but they’re used a bit differently:

täysi is a regular adjective: jono on täysi = “the queue is full.”
täynnä is very common in the sense “full (of something)” and can also stand alone: jono on täynnä = “the queue is full.”

If you add what it’s full of, Finnish strongly prefers täynnä + partitive:

Jono on täynnä tulostustöitä. = “The queue is full of print jobs.”

What part of speech/case is täynnä?

Learner-friendly way to think about it: täynnä behaves like a fixed predicative expression meaning full (often “full of …”). You don’t usually inflect it like a normal adjective in that position.

Practically:

You use olla + täynnä as a set pattern.
If you specify the “contents,” that noun is typically partitive (e.g., paperia, töitä, viestejä).

Why is there a comma before joten?

joten (“so/therefore”) links two clauses, and Finnish normally puts a comma before such coordinating/conclusive conjunctions.

Structure here:

Clause 1: Tänään tulostusjono on täynnä,
Clause 2 (result): joten lähetän tiedoston sähköpostitse.

How is joten different from koska?

They express different logic:

koska = because (gives the reason)
joten = so/therefore (gives the consequence)

Compare:

Lähetän tiedoston sähköpostitse, koska tulostusjono on täynnä.
“I’ll send the file by email because the print queue is full.”
Tulostusjono on täynnä, joten lähetän tiedoston sähköpostitse.
“The print queue is full, so I’ll send the file by email.”

Both are natural; they just flip what’s presented as the “main point.”

Why is it lähetän tiedoston (with -n), not lähetän tiedosto or lähetän tiedostoa?

That’s Finnish object case behavior:

tiedoston is the total object (often called “accusative-like”; it looks like genitive -n in the singular). It suggests you’re sending the whole file as a complete action.
tiedostoa (partitive) would suggest an incomplete/ongoing/indefinite amount, which fits poorly with “sending a file” as a completed package, but could work in some contexts (e.g., “I’m sending (some of) the file / I’m in the process of sending the file”).

So lähetän tiedoston is the default for “I’ll send the file.”

What does sähköpostitse mean, and why not sähköpostilla?

sähköpostitse means by email / via email and is a common adverbial form used for “by means of X.”

You can also say:

sähköpostilla = “by email” (more literally “with/using email”)
sähköpostin kautta = “through email”
sähköpostina = “as an email” (focuses on the form/message)

In everyday Finnish, sähköpostitse and sähköpostilla are both common; sähköpostitse can sound a bit more “method/means”-like or slightly more formal, depending on context.

Does lähetän mean “I send” or “I will send”? Where is the future tense?

Finnish has no dedicated future tense. The present tense often covers both:

lähetän = “I send” (habitual or immediate)
lähetän = “I will send” (future meaning inferred from context)

Here, with tänään and the situation described, it naturally reads as “so I’ll send the file by email.”