Major Description
While looking and running mime4J benchmarks, I tried some alternative implementations for Base64 encoding / decoding.
Base64InputStream proved to be 20% faster than its Java8 counterpart.
However, throughtput went from 280 MB/s to 520 MB/s by switching to Java8 Base64.getMimeEncoder().wrap(...)
Tests pass and this speeds up message writing operations... Apache James can for instance beneficiate of it when composing JMAP messages with large attachments.