I found that this was happening with my users when they would write a document in Word, then Word would automatically convert an email address into a clickable address, and the user then pasted all the content from Word into ActivEdit using the paste button. The ActivEdit 4 Word cleaner removes all o: prefixes -- which inadvertently turns "mailto:" into "mailt" The code that does this is in ae_cleanWord is:
newData = newData.replace(/o:/g, ""); // remove all o: prefixes
Using a modified version of the Word cleaner through the API, I surrounded this line with a simple fix:
newData = newData.replace(/mailto:/g, "TEMPMAILTO") // to prevent the o: prefix removal from breaking mailto:
newData = newData.replace(/o:/g, ""); // remove all o: prefixes
newData = newData.replace(/TEMPMAILTO/g, "mailto:") // restore the mailto
There's probably a more elegant way to do this but it's working fine for me.