Single-Character Names
Prior to V8.7 sendmail, the name
of a macro was required to be a single
character.[305] Any character can be used except the
{ character.
However, sendmail uses many
characters internally and requires that they serve
specific purposes. In general, only uppercase
letters should be employed as user-defined macro
names. Arbitrary use of other characters can lead to
unexpected results.
The character that is the macro’s name must be a
single-byte character. Multibyte international
characters have only the first byte (or last,
depending on the machine architecture) used for the
macro’s name, and what remains is joined to the
text.
The high (most significant) bit of the character is always cleared (set to zero) by sendmail.
[305] * Beginning with V8.7, both single- and multicharacter names can be used.
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