If you are using NowSMS with SSL/TLS in a server role, please be advised that OpenSSL is used to provide this functionality, and may be affected by the widely publicized “heartbeat” flaw.
To address this issue, an update for the module that provides SSL/TLS functionality (OpenSSL v1.0.1g) is available at http://www.nowsms.com/download/heartbeatfix.zip.
This download is a ZIP archive that contains a replacement version of SMSSSL.DLL, which should be compatible with any NowSMS version since 2012 (older versions would not be affected by this issue).
Stop the NowSMS services and exit the NowSMS configuration program before manually copying SMSSSL.DLL from this ZIP file over the old version. It may be advisable to first make a backup copy of the old SMSSSL.DLL in the unlikely event that the new version has unexpected certificate validation issues.