Use the following JCL to send email from mainframe using SMTPNOTE. There are other ways of sending emails as well.
Note:- Attachements can't be send using SMTPNOTE.
//STEP01 EXEC PGM=IKJEFT01,
// DYNAMNBR=250
//SYSPROC DD DSN=XXX.DSN.ALLOC.TO.SYSPROC,
// DISP=SHR
//SYSTSIN DD *
SMTPNOTE +
TO() +
CC() +
SU(SUBJECT HERE) +
DA('USERID.DSN.BODY.TEXT') BATCH
//SYSTSPRT DD SYSOUT=*
//SYSUDUMP DD SYSOUT=*