Any photographers about? Why do my images lose so much over the Internet?

[Olympiathequeen]

I photoshop as a hobby/business. I have an American client who loves to ask the impossible like making a 200x200 pixel photo blow up to a poster size! Well almost. He's lovely though.

Anyway I have been improving a very low resolution image and can print it out A4 with no pixelation or significant blurring, unlike the original image. I've got it to around 2000x2000 pixels 300dpi. I convert to jpeg and save at maximum (12). I sent it via google email but when he opened it, it was around 500x500 pixels on his monitor.

I am now trying PNG format but with the time difference and not being able to have a proper talk except in email, I can't figure it out.

What's happening and how can I fix it so that the images stay large?

Tia

Chances are your email program is compressing them as it sends. Can you use (e.g.) Dropbox or Google Drive to share them without email?

Im now sending via Dropbox and google drive. Also using TIFF files where it's appropriate. I think the receiver had a very low resolution monitor which made it look far worse,