The ‘ssl_error_bad_mac_alert‘ error typically occurs in Mozilla Firefox when affected users attempt to visit certain secured websites. In some cases, the error appears when the user attempts to send emails via the IMAP interface to Gmail. Below are the Genuine Cause of error.

3rd party Antivirus software is inspecting the HTTPS traffic – Although most Antivirus software is configured to do this by default, some end up being overprotective. Affected users report that they managed to resolve the issue after disabling HTTPS inspection (SSL Scan) from their 3rd party AV settings.
Chrome build is severely outdated – This particular issue is also reported to occur on machines running an outdated version of Chrome. However, this is only known to occur with every outdated Chrome version (build 40 and older)
Router’s MTU value is incompatible with the network configuration – The error is also confirmed to occur if the router’s MTU value is incompatible with the current network configuration. MIX*IT UP

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