quickBooks 18oo87I65O8 support number and does not start in windows 10

The problem that I mentioned has been solved by deactivating the email control of the antivirus; That way, all incoming and outgoing mail works smoothly.
But that has been done on two computers, one fixed and one portable and both receive and send without problems with a caveat that I do not know how to solve.
With both, having the antivirus email disabled, an email has been sent from another computer and enters the first one that opens, fixed or portable, and the other indicates "no new mail." How can I resolve this inconsistency? Thanks, I look forward to the solution.