I'm running FMS on the new macmini M1 in Big Sur (which I will point out is simply remarkable compared to my old xeon 12 core.  Many high resource functions are 40-80% faster)

However the new Base Elements plugin with native support for the M1 has a bug in BE_SMTPsend.  You cannot send to more than one email at a time now - and this broke a bunch of important scripts in my system.

Adding more than one email to either to: cc: or bcc: yields error 55.  I took me a whole day to find that this was the problem.

Assigning to a variable ($email = "[email protected], [email protected])  or just hardcoding in the command itself both give error 55 and fail.

Just a heads up.
my only solution is to loop though email address and send one at a time (or 3 at a time by using To: CC: and Bcc:)

did you try using semi-columns instead of comas?
Or maybe simply remove the blank after the coma.

$email = "email1@xx.xom;[email protected]"

yes, I've tried both.  I want to point out my code runs on all the other machines I have - it even runs on FMS 18.

It only doesn't run on my new M1 chip in Big Sur.

 

So this should be easy or reproduce, but I don't have a M1 chip with me

yeah, it should easy.  I've sent the Curl trace logs to Goya, but my problem with this is only on the M1.  Works well in all other environments.