If you are on Optus cable and are getting the following error while trying to send an email using Accountant Connect:
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The e-mail was unable to be sent due to: -3 - Couldn't connect to server:
bankrelay.myob.co.nz
Please remedy and try again
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then it is because Optus are blocking port 25 to reduce network spam relaying.
To re-enable it for yourself so that Accountant Connect can work, go to myaccount.optusnet.com.au/removemailfilter and follow the prompts.