Email skipped because it has previously bounced too many times

Many of our committee members over the past month cannot receive club emails sent from the website through our officers@maccabitoastmasters.org.au email address. When we send emails to this address, some of the members (including myself who is site administrator) get the following email response:

[members email address] was skipped because it has previously bounced too many times. Please visit support.toastmastersclubs.org and post a support request message for more information.

This is happening for the following members:
Leon Harari [ ldharari@gmail.com ]
Robyn Arya [ robynarya@gmail.com ]
Robyn Bavati [ robynbavati@gmail.com ]

The common theme for these office members is that they seem all to be gmail users. I do not know what to do to fix this. Please provide recommendations

seems your club was sent a virus by gabrielasantiago@cod-manila.com using the club contact email address.

SUCCESS (User Email) Mon 2020/02/10 10:34:15 UTC Club:[613630] From:[gabrielasantiago@cod-manila.com ()] To:[contact@maccabitoastmasters.org.au>ldharari@gmail.com] CC:[] Subject:[MELCO COPORATION PO ORDER]
SUCCESS (User Email) Mon 2020/02/10 10:34:16 UTC Club:[613630] From:[gabrielasantiago@cod-manila.com ()] To:[contact@maccabitoastmasters.org.au>robynbavati@gmail.com] CC:[] Subject:[MELCO COPORATION PO ORDER]
SUCCESS (User Email) Mon 2020/02/10 10:34:16 UTC Club:[613630] From:[gabrielasantiago@cod-manila.com ()] To:[contact@maccabitoastmasters.org.au>robynarya@gmail.com] CC:[] Subject:[MELCO COPORATION PO ORDER]

I have reset the bounce count
The Bounce Count for Email Address [ldharari@gmail.com] has been reset to zero.
The Bounce Count for Email Address [robynarya@gmail.com] has been reset to zero.
The Bounce Count for Email Address [robynbavati@gmail.com] has been reset to zero.

It would be wise to blacklist that sender's address to prevent this from happening again.