No support for RFC5321 4.5.2 Transparancy causing double periods

[AlexHaaniWink]

RFC5321 defines Transparancy in https://www.rfc-editor.org/rfc/rfc5321#section-4.5.2:

• Before sending a line of mail text, the SMTP client checks the
  first character of the line. If it is a period, one additional
  period is inserted at the beginning of the line.

• When a line of mail text is received by the SMTP server, it checks
  the line. If the line is composed of a single period, it is
  treated as the end of mail indicator. If the first character is a
  period and there are other characters on the line, the first
  character is deleted.

So, when a period character ends up at the start of a line in the e-mail source, the sending client will insert an extra period.
It's up to the SMTP server to remove that again.

So, if I have a url (either as normal text, or as attribute for an image or link) and one of its periods ends up at the start of a line, another period is added.
That extra period isn't stripped creating an invalid url.

Version I'm running should be the latest; Mailhog 1.0.1. But I'm not sure how I can verify that from my Docker container (which installs from here automatically and was built not more than a few months ago).