When deliver large mail, we can hit the errors as below:
An error occurred while transmitting to server name; memory allocation requests exceed 65000 bytes".
At present, the workaround is split the large group to small group, but it also has the size limitation:
Maximum number of recipients in a single mail message
For individual names and private groups which expand locally, 15KB; for public groups which expand on a server, 5MB
Detail in knowledge center:
So customer's expectation is: Hope no the limitation of large mail delivery or increase the field size.