So ever since I started playing Mabinogi, I've always come across the very noticeable lag problem. I would be envious of people being able to spam heal so fast when mine would take one heal per like three seconds.
I would ask around and most people would say to just buy another provider for my internet. Well I did and it didn't solve the problem (It did solve a lot of other problems though).

Back to the Point.

In order to possibly rid your Mabinogi of lag, I would suggest disabling your Nagle's Algorithm and lowing your MTU.

The wiki has a great guide on how to do it

Here's the link!
wiki.mabinogiworld.com/view/Lag#Disabling_Nagle.27s_Algorithm

Just click on the nagle's algorithm and MTU part of the index.

I hope I helped at least one or two people out because doing this helped me IMMENSELY !