I believe that this feature will assist to prevent undeliverable mails to postmaster.
Path: Tools > Manage Email Accounts > Edit Account > New Item Settings
Fill in the free text field "Ignore messages where the subject contains"

What is the format for the entries in to this field and what are the separators, please?
Will the following work:

postmaster;
out of the office;

Relates to post http://community.axosoft.com/forums/thread/12028.aspx

Hi Grant,

you need to have items on separate lines so in your scenario it would look like this.

postmaster
out of the office

Thanks,

Arash

Ok, thanks.
Is this case sensitive i.e. must the entries be exactly as they appear in the email subject line?

Hi Grant,

The entries posted in the field are not case sensitive.

Thanks,

Arash