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Use template tags when each sending account needs its own signature, link, or sender details. Sendmux substitutes values from the provider selected for that message in the subject, plain-text body, and HTML body.

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Set account variables

1

Open the account

Open Accounts and edit a sending account. For the managed Amazon SES account, select Edit variables from its menu.
2

Add a key and value

In Variables, add signature_url with the URL for that account. Select Save variables.
3

Use the tag

Insert [DP_VAR_SIGNATURE_URL] into your email template. Send a test message and inspect its delivered content and selected provider in Logs.
For example, use the variable in an HTML link:
All provider types support variables. On the shared Amazon SES account, variables are editable while protected connection settings stay locked.

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Key and value limits

Each account can store at most 50 keys. Keys contain 1–64 ASCII characters and must match ^[a-z][a-z0-9]*(?:_[a-z0-9]+)*$. Start with a lowercase letter; use lowercase letters, digits, and single underscores between nonempty segments. Leading, trailing, and repeated underscores are invalid. Each value is a string of at most 4,096 Unicode code points. An empty string is valid. To form a tag, uppercase the key and add the DP_VAR_ prefix inside brackets: signature_url becomes [DP_VAR_SIGNATURE_URL].

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Substitution rules

Valid custom tags whose keys are unset become empty strings. Values are inserted raw: Sendmux does not escape HTML, encode URLs, or expand template tags inside another value. Prepare each value for the context where you insert it. Subject substitutions remove control characters so a value cannot inject another email header. Body values retain their original content. Substitution supports plain text, HTML, quoted-printable, and base64 message content, including encoded subjects. Sendmux does not substitute template tags inside attachments, signed or encrypted message parts, or attached emails. Variables belong to the selected provider, not the recipient or credential. Passwords, access tokens, and other connection secrets have no built-in template tags.

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Built-in tags

These seven tags read the selected provider’s configured values: The sender-related tags read provider settings. An unset setting does not fall back to the sender supplied in your message.

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Edit several accounts

Select accounts in Accounts, then open Update Variables and choose a mode: When Replace all has no keys, select Confirm clear to remove all variables from the selected accounts, or Cancel clear to leave them unchanged. Limits apply to each resulting map, including keys already on the account. Review the reported failures after a bulk edit, then open an affected account to verify its values.

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Management API

The provider detail response includes variables, returning {} when unset. Include the optional map when creating a provider or updating it with PATCH /providers/{public_id}:
Omitting variables from a PATCH preserves the existing map. Supplying it replaces the map, and { "variables": {} } clears all keys. Provider list and delivery-group summaries omit variable values; fetch the provider detail when you need them.

Delivery groups

Restrict a message to providers in selected groups.

Sending accounts

Configure the providers that supply template values.