504 error

I have been getting 504 error page whenever I try to post a new entry. Being naive, I thought it was the admin cache causing the problem. But after deleting the cache files, modified some codes and activated plugins, the problem still persists. I made a post in my host’s support forum, the reply was:
“This effect is usually caused by timeout during sending e-mail notification. Workarounds are 1) change email provider that receives those notifications 2) disable them completely.”
I remove my email info from Options >> Writing Options. But where else should I remove? And is there any ways to disable the e-mail notification completely? Will there be any further problems caused by disabling it?