[vidarh]

My first question would be what archival requirements they have for e-mail.

Some governments have legal requirements for incoming official mail - whether on paper or electronic - to be printed off and stamped with the time and date, and manually entered into a journal and archived in multiple copies in separate locations for audit and open access purposes. Others may "just" require an electronic journal, but tend to still have very strict requirements on access, and particular security mechanisms to prevent modification of the journal.

Archival requirements can easily make up the vast majority of cost of processing mail if the rules are complicated enough.

Depending on the extent of "unusual" requirements like that, it may not be that bad. In any case, without more details about exactly what is included it's not very easy to assess whether or not the cost is unreasonable...