2.2.3.2.5 Importance

To set the value of the PidTagImportance property ([MS-OXCMSG] section 2.2.1.11), clients SHOULD write the value to an Importance header.

MIME readers map Importance header values to values of the PidTagImportance property as specified in the following table.

Importance header value

PidTagImportance property value

Low

0x00000000

Normal

0x00000001

High

0x00000002

Clients MAY<111> use a Priority, X-Priority, or X-MSMail-Priority header instead of an Importance header to set the value of the PidTagImportance property. In that case, MIME readers map the header values to values of the PidTagImportance property as specified in the following tables. However, if an Importance header is present, MIME readers SHOULD use its value in preference to any of the others.

Priority header value

PidTagImportance property value

Non-Urgent

0x00000000

Normal

0x00000001

Urgent

SHOULD be 0x00000002, MAY<112> be 0x00000001

X-Priority header value

PidTagImportance property value

5

0x00000000

4

0x00000000

3

0x00000001

2

0x00000002

1

0x00000002

X-MSMail-Priority header value

PidTagImportance value

Low

0x00000000

Normal

0x00000001

High

0x00000002