sibis_email To: appears broken in at least some use cases

[shippy]

For visual QC, the e-mail string is treated as if it contained a list of recipients, so "[email protected]" gets broken into [email protected], [email protected], ..., [email protected], [email protected], [email protected], [email protected].

[shippy]

The culprint is here - ",".join("aaa") will result in "a,a,a". We should check to_email is an instance of basestring and enclose it in a list if so, first.