Commit c67f922 breaks plain text mails in most mail clients

[Marcus Soll]

Hi,
unfortunately, the latest commit (c67f922) always adds an empty section Content-Type: text/html; charset=UTF-8 to each plain text mail. This breaks the display of the mail on most mail clients since html-mail is default on most and only an empty mail is displayed in html view.

I'm not an expert in emails, but I think the way to fix this issue would be to not write a MIME boundary at all if the part is missing instead of writing an empty MIME part. However, since I do not have a GMail account I can not verify if #61 would still be solved.

[Dom]

Ah I was afraid something like this would happen! Thank you for reporting it!

I had real trouble getting integration tests to deliver messages to gmail (likely because my test domain has DKIM/spf/etc) so couldn't reproduce the problem and kind of had to hope for the best. A bad strategy indeed.

I think not including the parts at all if they're empty makes sense - I'm happy to patch it this weekend or accept a PR if you fancy!

Thanks again,

Dom