Shuffle regularization for multiple Eisenstein series of level $N$

Bachmann and Tasaka discovered a relationship between multiple Eisenstein series (MES) of level 1 and formal iterated integrals corresponding to multiple zeta value. They also constructed shuffle regularized MES of level 1, which satisfies the shuffle relation that is same as multiple zeta values. In this paper, we expand their results for arbitrary level and give some linear relations among MES of level $N$.