wow this has been laying around for sooo long. current jessie version is 2.1.18 and that same line that was bugging is now #739
however, I've tried to reproduce the issue in jessie with the same list@domain and with different ones and I couldn't. I don't know if it could be linked to locale or other environment variables like this, though. in the context of that code, hostname would be initialized with this: hostname = ((mm_cfg.DEFAULT_URL and urlparse.urlparse(mm_cfg.DEFAULT_URL)[1]) or mm_cfg.DEFAULT_URL_HOST) the reported error would imply that no default URL can be found in the configuration.
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