UTF-7 (according to its RFC) isn't a "Unicode Transformation Format", as the definition can only encode code points in the BMP (the first 65536 Unicode code points, which does not include emojis and many other characters). However if a UTF-7 translator is to/from UTF-16 then it can (and probably does) encode each surrogate half as though it was a 16-bit code point, and thus can encode all code points. It is unclear if other UTF-7 software (such as translators to UTF-32 or UTF-8) support this.