There are some email use cases that cannot be supported with Templafy signatures from Email Signature Server due to Microsoft, other technical limitations, or they are unsupported by specific design decisions. Below are the tables listing these various use cases with some remarks on the nature of the limitation.
|Connector validation message||Sender is O365ConnectorValidation
|Message is Exchange calendar item||Contains header "X-MS-Exchange-Calendar-Series-Instance-Id"|
|Message contains calendar item||Signature placement here is undesired|
|Auto-generated message||Contains header "auto-generated"|
|Auto-reply message||Contains header "x-autoreply", "x-autorespond", "auto-replied"|
|Read receipt messages||"message/disposition-notification" message types|
|Microsoft Planner comments||Signature placement here is undesired|
|TNEF messages not marked as Email Message documents||When using TNEF as communication format, the message parsed might have different types. We are only considering the signature attachment for Email Messages|
|Plain Text Already processed by Templafy||Contains header "X-ProcessedByTemplafy"|
|RTF Already processed by Templafy||Contains header "X-ProcessedByTemplafy"|
|HTML Converted from RTF Already processed by Templafy||Contains header "X-ProcessedByTemplafy"|
Due to technical limitations
|Encrypted message||S/MIME and PGP/MIME protocols, no signature|
|End to end signed message||S/MIME and PGP/MIME protocols, no signature|
|Microsoft Information Protection labeled and encrypted messages||
no signature, can use "msip_labels" mail flow rule bypass
|RTF messages that do not provide the HTML version||For RTF, we request the HTML version using EWS or Graph API. In cases where this request fails, no signature can be added|
|Out of office / automatic forwarded emails with external forwarding feature enabled||Messages are sent but broken with winmail.dat attachment|
|Out of office with external forwarding disabled||emails are being blocked|
|RTF reply to email||
signature attached at the bottom
|Recall emails functionality fails||
Recall email function is itself implemented as an email. When these special Recall emails are forwarded to any Outbound Connector, the Recall functionality will fail. Can use mail flow rule bypass.
Additionally, any email forwarded to any Outbound Connector will not be able to be recalled later.
Active security feature
|Templafy secret key validation fails||RelayDenied response|
|DKIM verification fails||TransactionFailed response|
Issues caused by Mail Clients
- When sending RTF emails with in-lined images, the image quality is lost and the HTML format is broken. This is not related to Email Signature Server as it can be reproduced in any Microsoft 365 environment.