ezmlm, as far as we know, places no restrictions on character sets. The configurable default character set allows you to use other character sets for out going ezmlm messages. ezmlm-make does not per se support other character sets. However, any single-byte character set is supported, as long as the us-ascii character sequence ‘</’ does not occur anywhere as the first characters of the line, and the character sequence ‘<#x#>’ (where ‘x’ is any number, or A, B, C, D, F, H, L, R, T) does not occur anywhere is text (if it does, it risks being substituted). Also, any occurrence or ‘<#A#>’ and ‘<#R#>’ that is the first on any text line will be substituted by ezmlm-manage and ezmlm-store. Any occurrence of ‘!A’ and ‘!R’ as the first characters on a line will be substituted by ezmlm-manage and ezmlm-store.
For multi-byte character codes, the same restrictions apply. Thus, ‘</’ at the start of a line will confuse ezmlm-make, and any ‘<#x#>’ sequence within the text risks substitution. In practice, both of these should be very rare and easily avoidable when setting up an ezmlmrc(5).