Answer
No — this specific error code is a mail-relay/mailbox-permissions issue on the mail server side (commonly Exchange/Office 365), not an IFS Connect problem. It typically means the mail-sender account credentials configured in IFS don't match the specific From/sender address IFS is actually trying to send as — sending as an address that differs from the authenticated account is rejected by Exchange/Office 365 with exactly this error. Either configure the mail sender to authenticate as the same address it sends from, or set up an SMTP relay configuration on the mail-server side that explicitly permits the authenticated account to send as other addresses.