Replies are sometimes using ISO-8859-1character set

Hello,

I am using iCloud - and iCloud Mail - in OSX 10.10.2 Yosemite on Macs (several different Macs).

Sometimes -- rarely -- when I do a reply to all and I look at the reply I mailed out under the "Sent" tab, I see that the whole reply is "garbled".

Loads of A's and 0's.

The actual reply is preceded with a text that resembles this (the numbers change from reply to reply):

Quote

--Apple-Webmail-42--c10907ed-7ae8-475d-80.....followed by more numbers

Content-Transfer-Encoding: quoted-printable

Content-Type: text/plain;

charset=ISO-8859-1;

format=flowed

Unquote

The above "header" is followed by my reply that is completely garbled up too.

How can I avoid this formatting from happening?

Thanks in advance for your help.