Fix bug in parsing string with escape symbols in envelope.
Fix bug in parsing string with escape symbols in envelope.

jstedfast/MailKit,rajeshwarn/MailKit,jamie-dainton/MailKit,sstraus/MailKit,dsbenghe/MailKit,matt2003/MailKit,mganss/MailKit,FubarDevelopment/MailKit,nachocove/MailKit,eino-makitalo/MailKit