Pela definição abaixo, diria - comunicados ou mensagens, conforme traduzido na segunda referência.

- A transmittal is used to transfer the asset’s drawings, specifications, calculations and other information, usually for review, comment, ...
www.opentext.com/2/sol-products/sol-pro-docmgmt-collaborati... - 37k

- Note: You must have a different transmittal number for each permit application. Click the "Get Transmittal Number" button again for a new number. ...
www.mass.gov/dep/service/online/trasmfrm.shtml

- ALERTA: A informação contida nessa mensagem é confidencial, e destinada ao uso exclusivo do(s) destinatário(s)
referido(s) acima. Caso a presente tenha sido recebida por equívoco, notificamos que sua divulgação é proibida por
lei, e solicitamos que o remetente seja comunicado imediatamente, via Internet, ou via ligação telefônica a cobrar
para o número (55 11) 3049 3900. Obrigado.
NOTICE: This transmittal and/or attachments may be confidential or privileged communication. If you are not the
intended recipient, you are hereby notified that you have received this transmittal in error; any review, dissemination,
distribution or copying of this transmittal is strictly prohibited. If you have received this transmittal and/or attachments
in error, please notify us immediately by reply or by telephone (call us collect at (55 11) 3049 3900) and immediately
delete this message and all its attachments. Thank you.
-distribution or copying of this transmittal is strictly prohibited. If you have received this transmittal and/or attachments ...
www.bradespar.com.br/pdf/RRI/3RRI.pdf