The Ctrl+= hotkey increases the font size for the current session in mrxvt. What configuration option will increase the font size permanently?
If you are refering to the font size in the terminal in general, add these lines to your
Replace my font example (DejaVu Sans Mono) with your desired font and size.
Keep in mind that you can use
Personally I use the second method, but you can define different fonts in different terminals if you like.
Since version 0.3.9 mrxvt reads information about resources from ~/.mrxvtrc. Try putting your favorite font in ~/.mrxvtrc