<pid="rfc.section.4.1.4.p.5">Further processing by the Submission Entity normally depends on part of these Header Fields, e.g. From and Date HFs are required by <ahref="#RFC5322"class="xref">[RFC5322]</a>. Furthermore, not including certain Header Fields may trigger spam detection to flag the message and/or lead to user experience (UX) issues.</p>
<pid="rfc.section.4.1.4.p.6">For further Data Minimization, the value of the Subject Header Field SHOULD be obfuscated. In addition, the value of other Essential Header Fields MAY be obfuscated. Further Header Fields MAY be obfuscated, though simply not adding those to the Outer Message Header SHOULD be preferred over obfuscation. Header Field obfuscation is further specified in <ahref="#obfuscation-outer-HF"class="xref">Section 4.1.4.1</a>. Header Fields not obfuscated should contain the same values as in the Original Message.</p>
<pid="rfc.section.4.1.4.p.6">For further Data Minimization, the value of the Subject Header Field SHOULD be obfuscated. In addition, the value of other Essential Header Fields MAY be obfuscated. Further Header Fields MAY be obfuscated, though simply not adding those to the Outer Message Header Section SHOULD be preferred over obfuscation. Header Field obfuscation is further specified in <ahref="#obfuscation-outer-HF"class="xref">Section 4.1.4.1</a>. Header Fields not obfuscated should contain the same values as in the Original Message.</p>
<pid="rfc.section.4.1.4.p.7">The MIME Header Section part is the collection of MIME Header Fields describing the following MIME structure as defined in <ahref="#RFC2045"class="xref">[RFC2045]</a>. A MIME Header Section part typically includes the following Header Fields:</p>