Configuring additional outgoing mail servers

from the Apple support websites has detail instructions:

1. Go to Settings → Mail, Contacts, Calendars.

2. Tap the Mail account for which you would like to change the settings.

   If your account is configured to sync Notes or other items, you may need to tap Account Info on the following screen as well.

3. On the Account Info screen, locate the Outgoing Mail Server section and tap the existing SMTP entry.

4. A list of SMTP servers will appear, with the Primary Server and then Other SMTP Servers. Go to Other SMTP servers → Add Server....

   

5. Enter the additional SMTP server information. Host Name is required.

6. Tap Save.

Spotlight is now indexing the attachments :-). What I did is the following. (Not sure if it will solve anybody else his problems but you never know)

I wanted to know if the issue was Exchange specific so I made a new gmail account and sent an email with an attachment to that account. That attachment got indexed. I opened the attachment and then saw that it was located somewhere deep down in ~/Library/Mail. I then also checked if Attachments were really downloaded by the exchange client by looking for *.pptx files by running

find . -name "*.pptx"

in ~/Library/Mail. When I used spotlight after that I all of a sudden could find all attachments in email. So I guess adding the gmail account to mail triggered spotlight somehow