Seems to be still there in Simple Java Mail 6.5.0:
package org.simplejavamail.converter.internal.mimemessage;
MimeMessageParser : Line 508 :

public Map<String, DataSource> getAttachmentList() {
   return this.attachmentList;
}

WIll not work with two attachments named e.g.:
TSOL0038
TSOL0038.AUF

i.e. no suffix in one case.
This case is used for electronic billing for healthcare in Germany.
Works fine with different suffixes.

#249