They specify that I use port 21 in their documentation. I am able to backup to this same account using Plesk Backup Manager.
the error portion of the migration log:
INFO: The return code was
No output on STDOUT were performed by the utility
No output on STDERR were performed by the utility
[2014-10-30 14:52:18.351| 1901] INFO: ENV[LANG]=en_US.UTF-8
[2014-10-30 14:52:18.351| 1901] INFO: Executing utility: /usr/local/psa/admin/sbin/backup_sign --sign-dump /usr/local/psa/PMM/tmp/backupSDOBlx/clientdomainfolder --session-path=/usr/local/psa/PMM/sessions/2014-10-30-145215.970
[2014-10-30 14:52:18.364| 1906] INFO: backup_sign started : /usr/local/psa/admin/sbin/backup_sign --sign-dump /usr/local/psa/PMM/tmp/backupSDOBlx/clientdomainfolder --session-path=/usr/local/psa/PMM/sessions/2014-10-30-145215.970
[2014-10-30 14:52:18.380| 1906] INFO: backup_sign finished. Exit code: 0
[2014-10-30 14:52:18.381| 1901] INFO: The utility executed with the return code 0
[2014-10-30 14:52:18.381| 1901] INFO: Ftp init url ftp://filesanywhere.com/clientdomainfolder
[2014-10-30 14:53:21.445| 1901] INFO: CurlError[f70f602b-65f6-432a-879b-a0b72fa16894]: Curl error: Couldn't connect to server [./ftp.cpp:418]
void plesk::tFtpConnection::UploadFile(const std::string&)
[2014-10-30 14:53:21.445| 1901] INFO: TransportError[78b77289-deec-441e-8f87-a375a944abc3]: Transport error: unable to put local file /usr/local/psa/PMM/tmp/backupSDOBlx/clientdomainfolder to clientdomainfolder: Curl error: Couldn't connect to server [./transport.cpp:706]
virtual void plesk::tRepositoryFtp:
utFile(const std::string&, const std::string&)
[2014-10-30 14:53:21.446| 1901] INFO: pmm-ras finished. Exit code: 1