Line length issues in HTML email

[ewxrjk]

HTML email output may include an embedded image:

<p class=history><img class=history src="data:image/png;base64,iVBORw0KG...lFTkSuQmCC"></p>

In Exim this triggers the following diagnostic in mainlog:

mainlog.1:2018-12-25 17:55:02 1gbquz-0001CY-Tz DKIM: validation error: RSA_LONG_LINE
mainlog.1:2018-12-25 17:55:02 1gbquz-0001CY-Tz DKIM: Error while running this message through validation, disabling signature verification.

...and in panlclog:

2018-12-25 17:55:02 1gbquz-0001CY-Tz DKIM: signing failed: RSA_LONG_LINE

The message is delivered (in this case to GMail), it just doesn't have the DKIM signature added.

This seems like a bug in Exim, that it will accept a message that it cannot itself fully process, but maybe some more investigation is worthwhile.

[ewxrjk]

https://lists.exim.org/lurker/message/20120510.091222.2cf5d29b.en.html - someone else observes that Exim can't make its mind up about line lengths.