Does anyone know the rule, or even have a good guess, what causes GMail to put "message clipped" and a "see full message" link into some longer emails?
Is it text length? File size, with our without image sizes? Pixel height?
Apart from content being truncated, this also means some emails may be displayed without a footer, and therefore without an Unsubscribe link.
[NB: it's hard to search for "message clipped" because that appears in a LOT of web pages...]
The message is clipped once the body of your email markup is greater than ~100KB. Anything between <head> or <style> tags will get stripped and does not count towards the total amount.
Try removing tabs and spaces (and line breaks if you're feeling adventurous), I find this can account for 20-40% the total email markup.
That's great, thanks zerocents.
Have you got a citation for that or is it just something known in the industry?
It's right at 102kb. I've run various test where I had exactly 101kb in an email sent, it shows up. 102, and it clips, even if it's clipping a single line/character.
And yes, this includes commented material in the email.
That's terrific, thanks for that detail.
Just to add, that 102kb limit is only the file size limit of the html document, not including images!