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Thanks for all the replies. As a few have mentioned, directly or indirectly, this may well be an industry shift away from the long standing method of handling

by beezle 5y ago

Thanks for all the replies. As a few have mentioned, directly or indirectly, this may well be an industry shift away from the long standing method of handling temporarily undeliverable email, at least for the largest providers. This used to be the typical way of handling things: This is the mail system at host abc.xyz #################################################################### # THIS IS A WARNING ONLY. YOU DO NOT NEED TO RESEND YOUR MESSAGE. # #################################################################### Your message could not be delivered for more than 4 hour(s). It will be retried until it is 5 day(s) old. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. Bottom line seems to be, if you host your own email expect inbound mail to begin permanently failing after three hours should your server (or routing to it) be down longer.

toast0 5y ago
In theory, you might want to set up a secondary MX; although it might end up being too much work, as you need your secondary to do the same spam policies, and you want a copy of the valid destinations so you can refuse messages instead of bouncing them later.