SMTP Username must be less up to 60 characters

[mlopiccolo-progres]

Hi, our organization uses Azure Communication Services as SMTP.

ACS SMTP usernames are very long, ours is 88 characters, they are a string composed of various elements.

Could you raise this limit?

[rustdesk]

@fufesou, change to 300, check backend also please.

[mlopiccolo-progres]

Thank you!