Michael Santovec wrote:

Is your message format Plain Text or HTML?

With plain text, the final message should generally be not much larger
than the inserted text. If you are using anything other than English,
then there can be more overhead. For example, with
MIME/Quoted-printable encoding, accented characters can result in 3
characters in the message. And Unicode languages can have similar
overhead, but for every character.

If you are using HTML format, the message will be a minimum of twice the
size of the text. That's because there will both plain text and HTML
copies in the message. And the HTML tags will add much more.

Take a look at the message source (Ctrl-F3) for one of your sent
messages. You will see what is actually being sent.

And if shakey is adding a signature, especially one with an image, then
that would account for more the doubling in size when sending in HTML
format.