Using Media Encoder to make MP4 file

Hi!

I am trying to take my file from After Effects and usng Media Encoder, make it into an MP4 file, when I do this is produces a 3gp file, which I see is similar to an MP4, but the quality is absolutely terrible compared to the animation in AF. This video is going to be used for business purposes online and MP4 is the most convenient, so I do not have wiggle room in changing the file type. Any help would be appreciated in how to use the encoder correctly. 

Thanks

Cameron