Extra "\n " in Mandrill raw_message break some links

We typically see this kind of issue with SMTP libraries or frameworks that generate HTML with no true line breaks. The SMTP specs state that the line length for email shouldn't exceed 1000 characters. When that limit is reached, a line break gets inserted automatically when the message data is being transmitted over SMTP. This unfortunately often happens right in the middle of a word or a URL, for example. You'll want to take a look at your SMTP library to see if you can modify how line breaks are being handled.

If you're using HTML line breaks like <br> that are being used to indicate a break, those unfortunately won't help in this case. Adding your own line breaks (not HTML line breaks, but actual line breaks in the data such as a newline or end of line - usually \r\n - will help ensure that the forced line breaks aren't arbitrarily added in the SMTP conversation in inconvenient places.