I'm having the same issue with both outlook and mail.app
I have also searched the web for solution everywhere and what causes problems are when you:
- Make tab's between words.
- Use different font sizes.
- add images in the middle of text.
I like to use Century Gothic as a font and use the work around to send all text in my signature only.
When sending in either mail.app or outlook in Century Gothic the sizes send and recieve are different but always the same which is as follows (in signature only):
Font size 8 send = recieved font size 8.
Font size 9 send = recieved font size 13.
Font size 10 send = recieved font size 10.
Font size 11 send = recieved font size 11.
Font size 12 send = recieved font size 18.
Font size 14 send = recieved font size 14.
When I send the e-mails in any of the above sizes it will look as the same size as it should be on my mac.
However when someone read's for them it will be in the wrong size (second size).
When they reply my own e-mail back and I recieve it the sizes will be wrong as well (second size).
always the same ratio.
The above sizes are only when writing in signature.
If your writing in the body the sizes are also mismatching but at different values.
This leaves the issue that you should either always write in the signature, or always write the entire message in the body including the signature.
What I found on forums so far is that this is not a problem of mail clients but has something to do with how Mac font's get translated to windows, from windows to Mac there is no issue.
I'm not a computer expert or native english speaker (excuse me if there are any grammar mistakes).
But I hope this can somewhat help those that are dealing with this issue.