Sudden errors with SMTP

Errors appearing suddenly. as follows:
using 8.2.1473 (04b618f) no changes made prior to receiving this message

any idea why my own email sent to myself and others bounce this error?

[SMTP]Cannot send message (‘From’ field address ‘’ not accepted due to the following reason:
"5.1.0 blocked. Please see for more information. AUP#Out-1300

Have you clicked on the “” link? A quasi-explanation can be found there…

sábado 21 agosto 2021 :: 1708hrs (UTC +01:00)

Hi @Tharman55

This not an eMC error, apparently Spectrum impose limits?

See below:

Spectrum limits the number of concurrent connections from a sender, as well as the total number of connections allowed. Limits vary based on the reputation of the IP address. Reduce your number of connections and try again later.

¡Saludos desde la soleada España!
¡Mis mejores deseos y mantente a salvo!