[SMTP] Two response codes returned for end of data command

[Majora-OX]

Sending a '.' to the SMTP server to signal the end of the DATA command seems to have two response codes be returned at the same time, instead of just one.

For example I'm seeing this when sending an email through the SMTP server:

Sent to SRV: 'DATA'
Received from SRV: '354'
{Sending & receiving message contents}
Sent to SRV: '.'
Received from SRV: '250'
Received from SRV: '250 Ok {Email UUID}'

This ends up causing errors for me when trying to send multiple emails at the same time.
Am able to replicate the issue on v1.13.2