Merhabarlar! 

I have this question regarding the passive tense, the word ´ödendi´ means it was paid, a classic passive tense, but how come Yapmak´s passive tense is ´yapıldı´, Göndermek--  Gönderildi, I was told the verb conjugation of Turkish is very regular, is this an exception to the rule? please help me solve this puzzle!

My Turkish friend helped me understand the above question, it seems that when passive tense comes across the letter e, il just don´t apply.

Right!

after vowels and l you need to use -n- istead of -il- which is used otherwise:

bil-mek -> bil-in-mek (after l)

de-mek -> de-n-mek (after a vowel)

öde-mek -> öde-n-mek (after a vowel)