Persons with serious mental illness (SMI) die on average 10-15 years earlier than those in the general population. Smoking is the strongest risk factor for their elevated mortality. Helping SMI smokers to quit is an urgent and unmet need. The hospital is an optimal setting to provide smoking cessation services. Hospital admissions for SMI are common with more than 1.2 million inpatient stays for schizophrenia and mood disorders per year in the US. Hospitalized patients experience required abstinence, are available for counseling, and can try cessation medications in a supportive setting. The challenge is how to engage SMI patients in cessation services post-discharge. An easy-to-access digital intervention is a scalable and sustainable way to bridge the inpatient-to-outpatient gap and to promote sustained abstinence. Digital interventions can deliver all elements of cessation treatment and yield quit rates comparable to face to face and telephonic interventions. SMI patients use and benefit from technology-based interventions but currently there is no digital smoking cessation program addressing their needs. In this study, the investigators tested a digital intervention adapted to the needs of SMI smokers and to being introduced in the inpatient psychiatric setting. The digital intervention, BecomeAnEX (EX), developed and run by Truth Initiative for over 10 years, includes real-time one on one coaching via live chat, nicotine replacement therapy decision support and delivery, personalized quit plans, a large online social network for peer support, a robust and fully integrated text message program, and tailored email messaging. SMI smokers recruited during psychiatric hospitalization will be randomized to usual care or to an adapted version of EX (EX-SMI) and followed for 3 months after the hospital stay. The investigators will compare the feasibility/acceptability of EX-SMI, measure intervention impact on target mechanisms, and obtain initial estimates of efficacy on 7-day point prevalence abstinence. Such an intervention could bridge the inpatient to outpatient gap in cessation services and will help people remain abstinent following hospital discharge.