Signature image size changing on replied emails

Signature image size changing on replied emails

Hi,

Sometimes I see the size of the image I use as signature changes when I open replied emails. Do you know why is this happening? It doesn't seem to happen when I send emails to Gmail though.

Signature should look like in attachment "Signature_normal.jpg" but it acually looks like this in attachment "Signature_big.jpg" in some cases.