Hi Thank you for your question, but I do not think that this is related to the Firefox web browser. You should be able to change this in user facing settings with your email service provider. This will be different for different providers, but should be fairly straightforward to do. This [https://support.mozilla.org/en-US/kb/problems-with-email-how-to-find-help article] should help point you in the right direction. I also notice that you are using an older version of Firefox. I strongly recommend you update to make sure you have any security and stability fixes, as well as new features. You can read more about how to update [https://support.mozilla.org/en-US/kb/update-firefox-latest-version here]. I hope this helps, but if not, please come back here and we can look into a different solution for you.