Tā yígòng fā le sān fēng yóujiàn gěi wǒ.

It means in total / altogether. The most natural placement is after the subject and before the main verb phrase.

• Very natural: 她一共给我发了三封邮件。 (Tā yígòng gěi wǒ fā le sān fēng yóujiàn.)
• Also fine: 她一共发了三封邮件给我。
• Less common but acceptable: 她给我一共发了三封邮件。
• Avoid putting 一共 right between the verb and its object: 她发了一共三封邮件 (unnatural).

Yes, but it changes the meaning:

• 了: a specific completed event or total within a specific frame/context.
  Example: 她一共给我发了三封邮件。 (She sent me three in total [in that context].)
• 过: an experiential meaning (has ever done).
  Example: 她给我发过三封邮件。 (She has sent me three emails at some point before.) You can combine 一共 with 过 to mean “so far in my experience”: 她一共给我发过三封邮件。

You can, especially with 已经 to stress a current state/result:

• 她已经给我发了三封邮件了。 You’ll also hear: 她已经给我发三封邮件了。 (dropping the verb‑level 了 and keeping sentence‑final 了). Both are idiomatic.

封 is the standard classifier for letters and emails. Use it when counting individual emails:

• 三封邮件 = three emails. Other classifiers are not appropriate here. For text messages you’d use 条, for phone calls 通.

Here 给 (gěi) functions as a coverb/preposition introducing the recipient (“to/for”):

• 给我发 = send to me. It’s not the main verb in this sentence; 发 is.

All of these are common:

• 她一共给我发了三封邮件。 (very common colloquial order)
• 她一共发了三封邮件给我。 (also fine)
• 她把三封邮件发给了我。 (uses 把, highlighting the object) They’re all grammatical; the first is the most conversational.

You can treat 发给 as a disyllabic verb (“send to”). Put 了 after the verb:

• Correct: 她发给了我三封邮件。
• Also correct (with the other common pattern): 她给我发了三封邮件。
• Avoid: 她发给我了三封邮件。 (placing 了 after 我 is unnatural)

No. 对 works with verbs like 说 (speak to), 笑 (smile at), 有帮助 (be helpful to), etc. For sending to someone, you want 给:

• Correct: 给我发邮件
• Incorrect: 对我发邮件

Yes. 写 focuses on the writing/composition, while 发 focuses on the sending/transmission. In real life, people often say either:

• 她给我写了三封邮件。 (she wrote me three emails)
• 她给我发了三封邮件。 (she sent me three emails) If you want to be precise: she might write but not send; 发 guarantees it was sent.

Common options:

• General past negation: 她没(有)给我发邮件。 (She didn’t send me email.)
• Stress no occurrence ever (up to now): 她没(有)给我发过邮件。
• Emphasize “not even one”: 她一封邮件也没给我发。

Drop the perfective 了 and add a future/intent marker:

• 她明天会给我发三封邮件。 (will)
• 她打算给我发三封邮件。 (plans to) For ongoing/habitual description, you can also use the bare form with context:
• 她经常给我发邮件。

Not really. Instead, express it from the receiver’s perspective with 收到:

• 我收到了她的三封邮件。 (I received three emails from her.) A 被-passive would sound odd here.

Tone sandhi:

• 一 becomes yí before a 4th-tone syllable (共 is 4th), so 一共 is yígòng.
• 给我 is two 3rd tones, so the first becomes 2nd: pronounce it géi wǒ (though it’s written gěi wǒ).

Chinese generally requires a classifier between numbers and countable nouns. The pattern is Number + Measure word + Noun:

• 三封邮件 (correct)
• 三邮件 (unnatural)

They’re near-synonyms meaning in total/altogether. Both work:

• 她一共给我发了三封邮件。
• 她总共给我发了三封邮件。 Any difference is minimal; 总共 can sound slightly more colloquial in some regions, but both are widely used.