Learn Dutch: Ik heb de correspondentie omtrent de hypotheek gelezen. - I have read the correspondence concerning the mortgage.

The preposition omtrent means 'concerning' or 'regarding' and is highly formal. While it means exactly the same thing as over ('about') in this context, you will almost exclusively see omtrent in official letters, business emails, or legal documents. In daily conversation, a Dutch speaker would just say de correspondentie over de hypotheek.

Could I use the other formal prepositions inzake or aangaande in this sentence?

Yes, they are almost entirely interchangeable in this context. aangaande ('regarding') works perfectly here. inzake ('in the matter of' or 'concerning') is also acceptable, though it is even more closely associated with legal or administrative jargon. For a bank letter about a mortgage, any of the three would be natural.

Why doesn't the past participle gelezen come right after the helping verb heb?

In Dutch main clauses, the conjugated verb (heb) takes the second position, but all other verbs, including past participles like gelezen, are pushed to the very end of the sentence. The entire phrase de correspondentie omtrent de hypotheek acts as the direct object, so it stays together as a single block of information and must come before that final verb.