We have a emailing list we send out to set of subscribers which have the option of unsubscribing. The method used for unsubscribing involves a reply from the unsubscriber where mailing program looks in the particular mail box to check for unsubscribe requests. It looks for a specific string with something of the utterance of "please unsubscribe me, blah, blah, blah". Granted, we suspected that not all unsubscribing requests will come in as prescribed, but we noticed a number of them are coming back with any space characters getting replaced with plus sign which comes back as "please+unsubscribe+me,+blah,+blah,+blah".
As an exchange admin, I don't know of anything that could be changing the text as it's coming in as far as exchange is concerned. Has anybody seen this before? Is this an email client issue, an email/spam/virus appliance issue, or other email servers like postfix. About every 1 out of 20 comes in like this.