MEXEM does not make margin calls. Real-time liquidations occur when your account has a margin deficiency. Generally, accounts will not have time to deposit funds to meet a margin deficiency. MEXEM sends margin deficit notifications on a best efforts basis, but this is not always possible in a fast moving market.
In order to determine if your account is margin compliant you should monitor Excess Liquidity and your Special Memorandum Account (SMA). You can see these values in TWS from menu Account, Account Window in section Available for Trading.
Additional information on: Available for Trading values can be found in the TWS Users' Guide.
You can also review our Margin Requirements and the Margin Education Center on the MEXEM website and learn about Margin Requirements in TWS Account Window in our MEXEM Short Video.