Not being able to send emails

not able to send emails, the problem started 4 days ago, then resolved itself with no action on my part and now the same problem arose again.
The Log Error message reads “Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond…”

Have been sending both to and and other email addresses

Version 8.2.1721