In the computer input context punctuation can cause problems. This makes it clear that the period does not go in the password box. Some email software only understands plain text. Italics, bold, and color changes will show up as control sequences in the text. Joe, I loved the presentation you gave to Walt this morning.
Web documents are particularly difficult to read with older email software.
Many people like to use different colors, sizes, and fonts in their email messages. A professional email message looks professional. Limit the variety. A Sans Serif font such as Arial can most likely be read by any email software and looks clean and professional. Mailing Lists, Listserv, Newsgroups, and Chat Groups Participating in a listserv, forum, or discussion group is one of the delights of the Internet.