On the Scanning Criteria tab, click Advanced.

Select Message size is in the criteria list.

Select > or <= from the comparison drop-down list.

Select > to apply the rule to messages that are larger than the specified size.
Select <= to apply the rule to messages that are smaller than or equal to the specified size.

For example, <= 10 MB applies the rule to all messages that are smaller than or equal to 10 megabytes.

Type a number for the size.

Select a unit of measurement from the following choices:

KB: Kilobytes
MB: Megabytes

Note:

The Message size is criteria is applied to the total size of a message, including any attachments it might contain.

For example, if a message contained two attachments, one a 3 MB attachment and the other a 1 MB attachment, a rule that deletes messages over 2 MB would delete the entire message, including both attachments.

Using Message Size Criteria