I forgot to mention I am trying to use either Safari or latest Firefox to open gmail.  Thanks

The passphrase is set by the hushmail sender. Maybe it's a default setting and she forgot to uncheck the option when sending the e-mail. Does she mention the passphrase anywhere in her ad or website? (I doubt it.) You probably need to ask her for the pass or ask her to send again without authentication.

Hushmail has
Encrypt Message  She need to disable that function
when replys e mail
Hope she is aware of that or there no much you can do
Take Care
CC

There are only one option in this case, she has to send you the passphrase to decrypt. Nothing else will work.

There 3 options with Hushmail, (1) send encrypted mail with a passphrase, (2) send encrypted mail w/o a passphrase to non-hushmail user; (3) send without encryption.

It is easy to make mistake with encryption and passphrase because it is the default setting. Your problem has nothing to do with MacBook, or Safari. Hushmail works with both and Mac Mail. I use to use it a while ago but $35/Mo got little steep for what I used it for.

Thanks for you replies. Still working on the problem but one came through I can read.  Progress!