I manage my own e-mail server. I occasionally have outbound messages rejected because my hosting provider's entire network sometimes appears on block/deny lists. I also have an e-mail account hosted by Microsoft Exchange Online. Yesterday, an outbound message from that account was rejected by a receiving server because the IPv4 address of one or more of Microsoft's servers was on a public block list.

Perhaps having multiple addresses hosted by different providers is now becoming a practical necessity.
#email #smtp #security