[Typo3] direct mail problems

[Michael Stein]

Dear list,
I don't understand many things in direct mail:
If I send my newsletter via mass-mail the following happens:
1. in plaintext I find a template that is not filled out
2. in the html-part I'm missing many pictures and grafics.
3. the plaintext and htmlmail are iso-8859-1 encoded and not utf-8

more questions:
How can I set the sender (From-field) for the subscription-mail  (who and where is this mail generated)?
What is happening when I klick to "invoke mailengine" (which script is invoke and who is collecting all the newsletterstuff)?

I'm open for all suggestions

Thanx Michael