451 4.7.500

Exchange Online returning 451 “Server busy” errors across Europe

We're seeing an increasing number of temporary mail-delivery failures when sending to Exchange Online recipients in Europe. The error is usually "451 4.7.500 Server busy. Please try again…

Exchange Online is returning “451 4.7.500 Server busy” across Europe

We're seeing an increasing number of temporary mail-delivery failures when sending to Exchange Online in Europe. The error is usually "451 4.7.500 Server busy. Please try again later,"…