How to get rid of "Show trimmed content" in GMail HTML emails?
I've just encountered this problem myself, and from my investigations it seems that GMail does indeed trim the content if it is similar to the preceding emails.
My solution is simply to insert the current time stamp at the end of every email:
[15:02:21 29/01/2013] End of message.
Voilà! Finally after long testing I have found a solution to this problem.
What Gmail does is it puts in the "Show Trimmed Content" option if the message is similar to previous ones, or the subject of the email appears as it is in the content of the email.
To avoid this, simply try inserting any randomly generated string inside your mail which will make your email messages different and will not let Gmail insert the Show Trimmed Content option.
To prevent this in HTML emails I'm adding two invisible unique elements: in the beginning and at the end of the mail. Like this:
...
<body>
<!-- this ensures Gmail doesn't trim the email -->
<span style="opacity: 0"> {{ randomness }} </span>
...
<!-- this ensures Gmail doesn't trim the email -->
<span style="opacity: 0"> {{ randomness }} </span>
</body>
{{ randomness }} is being replaced by my templating engine with the value of Date.now() (I'm using node.js, could be anything producing unique output)