Configure Attachment Blocking in Outlook Web Access

Oullok Web Access stores data about file extensions in the following registry keys:

Location: HKLM\System\CurrentControlSet\Services\MSExchangeWeb\OWA
Value: Level1FileTypes
Type: REG_SZ
Value Data: ade, adp, app, asx, bas, bat, chm, cmd, com, cpl, crt, csh, exe, fxp, hlp, hta, inf, ins, isp, js, jse, ksh, lnk, mda, mdb, mde, mdt, mdw, mdz, msc, msi, msp, mst, ops, pcd, pif, prf, prg, reg, scf, scr, sct, shb, shs, url, vb, vbe, vbs, wsc, wsf, wsh

Location: HKLM\System\CurrentControlSet\Services\MSExchangeWeb\OWA
Value: Level2FileTypes
Type: REG_SZ
Value Data: ade, adp, asx, bas, bat, chm, cmd, com, cpl, crt, exe, hlp, hta, htm, html, htc, inf, ins, isp, js, jse, lnk, mda, mdb, mde, mdz, mht, mhtml, msc, msi, msp, mst, pcd, pif, prf, reg, scf, scr, sct, shb, shs, shtm, shtml, stm, url, vb, vbe, vbs, wsc, wsf, wsh, xml, dir, dcr, plg, spl, swf

In order to add\remove file ext, simply change those Value data settings