Postmark API errors as seen here: https://postmarkapp.com/developer/api/overview#error-codes

postmark-api-errors-map.json

{
	"10": "Bad or missing API token",
	"100": "Maintenance",
	"300": "Invalid email request",
	"400": "Sender Signature not found",
	"401": "Sender signature not confirmed",
	"402": "Invalid JSON",
	"403": "Incompatible JSON",
	"405": "Not allowed to send",
	"406": "Inactive recipient",
	"409": "JSON required",
	"410": "Too many batch messages",
	"411": "Forbidden attachment type",
	"412": "Account is Pending",
	"413": "Account May Not Send",
	"429": "Rate Limit Exceeded",
	"500": "Sender signature query exception",
	"501": "Sender Signature not found by id",
	"502": "No updated Sender Signature data received",
	"503": "You cannot use a public domain",
	"504": "Sender Signature already exists",
	"505": "DKIM already scheduled for renewal",
	"506": "This Sender Signature already confirmed",
	"507": "You do not own this Sender Signature",
	"510": "This domain was not found",
	"511": "Invalid fields supplied",
	"512": "Domain already exists",
	"513": "You do not own this Domain",
	"514": "Name is a required field to create a Domain",
	"515": "Name field must be less than or equal to 255 characters",
	"516": "Name format is invalid",
	"520": "You are missing a required field to create a Sender Signature.",
	"521": "A field in the Sender Signature request is too long.",
	"522": "Value for field is invalid.",
	"600": "Server query exception",
	"601": "Server does not exist",
	"602": "Duplicate Inbound Domain",
	"603": "Server name already exists",
	"604": "You don't have delete access",
	"605": "Unable to delete Server",
	"606": "Invalid webhook URL",
	"607": "Invalid Server color",
	"608": "Server name missing or invalid",
	"609": "No updated Server data received",
	"610": "Invalid MX record for Inbound Domain",
	"611": "InboundSpamThreshold value is invalid. Please use a number between 0 and 30 in increments of \t5.",
	"700": "Messages query exception",
	"701": "Message doesn't exist",
	"702": "Could not bypass this blocked inbound message, please contact support.",
	"703": "Could not retry this failed inbound message, please contact support.",
	"800": "Trigger query exception",
	"809": "No trigger data received",
	"810": "This inbound rule already exists.",
	"811": "Unable to remove this inbound rule, please contact support.",
	"812": "This inbound rule was not found.",
	"813": "Not a valid email address or domain.",
	"900": "Stats query exception",
	"1000": "Bounces query exception",
	"1001": "Bounce was not found.",
	"1002": "BounceID parameter required.",
	"1003": "Cannot activate bounce.",
	"1100": "Template query exception.",
	"1101": "Template not found.",
	"1105": "Template limit would be exceeded.",
	"1109": "No Template data received.",
	"1120": "A required Template field is missing.",
	"1121": "Template field is too large.",
	"1122": "A Templated field has been submitted that is invalid.",
	"1123": "A field was included in the request body that is not allowed.",
	"1125": "The template types don't match on the source and destination servers.",
	"1130": "The layout template cannot be deleted because it has dependent templates using it.",
	"1131": "The layout content placeholder must be present in the layout HTML and/or Text body exactly \tonce.",
	"1221": "The 'MessageStreamType' associated with this request was invalid.",
	"1222": "A valid 'ID' must be provided.",
	"1223": "A valid 'Name' must be provided.",
	"1224": "The 'Name' is too long, it is limited to 100 characters.",
	"1225": "You have reached the maximum number of message streams for this server.",
	"1226": "The message stream for the provided 'ID' was not found.",
	"1227": "The 'ID' must be a non-empty string starting with a letter of the English alphabet.",
	"1228": "A server can only have one inbound stream.",
	"1229": "You cannot archive the default transactional and inbound streams.",
	"1230": "The 'ID' provided already exists for this server.",
	"1231": "The 'Description' is too long, it is limited to 1000 characters.",
	"1232": "You cannot unarchive this message stream anymore.",
	"1233": "The 'ID' must not start with the 'pm-' prefix.",
	"1234": "The 'Description' must not contain HTML tags. The characters '<' and '>' are not allowed.",
	"1235": "The 'MessageStream' provided does not exist on this server.",
	"1236": "Sending is not supported on the supplied 'MessageStream'.",
	"1237": "This 'ID' is reserved."
}

postmark-api-errors.json

[
	{
		"code": 10,
		"message": "Bad or missing API token"
	},
	{
		"code": 100,
		"message": "Maintenance"
	},
	{
		"code": 300,
		"message": "Invalid email request"
	},
	{
		"code": 400,
		"message": "Sender Signature not found"
	},
	{
		"code": 401,
		"message": "Sender signature not confirmed"
	},
	{
		"code": 402,
		"message": "Invalid JSON"
	},
	{
		"code": 403,
		"message": "Incompatible JSON"
	},
	{
		"code": 405,
		"message": "Not allowed to send"
	},
	{
		"code": 406,
		"message": "Inactive recipient"
	},
	{
		"code": 409,
		"message": "JSON required"
	},
	{
		"code": 410,
		"message": "Too many batch messages"
	},
	{
		"code": 411,
		"message": "Forbidden attachment type"
	},
	{
		"code": 412,
		"message": "Account is Pending"
	},
	{
		"code": 413,
		"message": "Account May Not Send"
	},
	{
		"code": 429,
		"message": "Rate Limit Exceeded"
	},
	{
		"code": 500,
		"message": "Sender signature query exception"
	},
	{
		"code": 501,
		"message": "Sender Signature not found by id"
	},
	{
		"code": 502,
		"message": "No updated Sender Signature data received"
	},
	{
		"code": 503,
		"message": "You cannot use a public domain"
	},
	{
		"code": 504,
		"message": "Sender Signature already exists"
	},
	{
		"code": 505,
		"message": "DKIM already scheduled for renewal"
	},
	{
		"code": 506,
		"message": "This Sender Signature already confirmed"
	},
	{
		"code": 507,
		"message": "You do not own this Sender Signature"
	},
	{
		"code": 510,
		"message": "This domain was not found"
	},
	{
		"code": 511,
		"message": "Invalid fields supplied"
	},
	{
		"code": 512,
		"message": "Domain already exists"
	},
	{
		"code": 513,
		"message": "You do not own this Domain"
	},
	{
		"code": 514,
		"message": "Name is a required field to create a Domain"
	},
	{
		"code": 515,
		"message": "Name field must be less than or equal to 255 characters"
	},
	{
		"code": 516,
		"message": "Name format is invalid"
	},
	{
		"code": 520,
		"message": "You are missing a required field to create a Sender Signature."
	},
	{
		"code": 521,
		"message": "A field in the Sender Signature request is too long."
	},
	{
		"code": 522,
		"message": "Value for field is invalid."
	},
	{
		"code": 600,
		"message": "Server query exception"
	},
	{
		"code": 601,
		"message": "Server does not exist"
	},
	{
		"code": 602,
		"message": "Duplicate Inbound Domain"
	},
	{
		"code": 603,
		"message": "Server name already exists"
	},
	{
		"code": 604,
		"message": "You don't have delete access"
	},
	{
		"code": 605,
		"message": "Unable to delete Server"
	},
	{
		"code": 606,
		"message": "Invalid webhook URL"
	},
	{
		"code": 607,
		"message": "Invalid Server color"
	},
	{
		"code": 608,
		"message": "Server name missing or invalid"
	},
	{
		"code": 609,
		"message": "No updated Server data received"
	},
	{
		"code": 610,
		"message": "Invalid MX record for Inbound Domain"
	},
	{
		"code": 611,
		"message": "InboundSpamThreshold value is invalid. Please use a number between 0 and 30 in increments of \t5."
	},
	{
		"code": 700,
		"message": "Messages query exception"
	},
	{
		"code": 701,
		"message": "Message doesn't exist"
	},
	{
		"code": 702,
		"message": "Could not bypass this blocked inbound message, please contact support."
	},
	{
		"code": 703,
		"message": "Could not retry this failed inbound message, please contact support."
	},
	{
		"code": 800,
		"message": "Trigger query exception"
	},
	{
		"code": 809,
		"message": "No trigger data received"
	},
	{
		"code": 810,
		"message": "This inbound rule already exists."
	},
	{
		"code": 811,
		"message": "Unable to remove this inbound rule, please contact support."
	},
	{
		"code": 812,
		"message": "This inbound rule was not found."
	},
	{
		"code": 813,
		"message": "Not a valid email address or domain."
	},
	{
		"code": 900,
		"message": "Stats query exception"
	},
	{
		"code": 1000,
		"message": "Bounces query exception"
	},
	{
		"code": 1001,
		"message": "Bounce was not found."
	},
	{
		"code": 1002,
		"message": "BounceID parameter required."
	},
	{
		"code": 1003,
		"message": "Cannot activate bounce."
	},
	{
		"code": 1100,
		"message": "Template query exception."
	},
	{
		"code": 1101,
		"message": "Template not found."
	},
	{
		"code": 1105,
		"message": "Template limit would be exceeded."
	},
	{
		"code": 1109,
		"message": "No Template data received."
	},
	{
		"code": 1120,
		"message": "A required Template field is missing."
	},
	{
		"code": 1121,
		"message": "Template field is too large."
	},
	{
		"code": 1122,
		"message": "A Templated field has been submitted that is invalid."
	},
	{
		"code": 1123,
		"message": "A field was included in the request body that is not allowed."
	},
	{
		"code": 1125,
		"message": "The template types don't match on the source and destination servers."
	},
	{
		"code": 1130,
		"message": "The layout template cannot be deleted because it has dependent templates using it."
	},
	{
		"code": 1131,
		"message": "The layout content placeholder must be present in the layout HTML and/or Text body exactly \tonce."
	},
	{
		"code": 1221,
		"message": "The 'MessageStreamType' associated with this request was invalid."
	},
	{
		"code": 1222,
		"message": "A valid 'ID' must be provided."
	},
	{
		"code": 1223,
		"message": "A valid 'Name' must be provided."
	},
	{
		"code": 1224,
		"message": "The 'Name' is too long, it is limited to 100 characters."
	},
	{
		"code": 1225,
		"message": "You have reached the maximum number of message streams for this server."
	},
	{
		"code": 1226,
		"message": "The message stream for the provided 'ID' was not found."
	},
	{
		"code": 1227,
		"message": "The 'ID' must be a non-empty string starting with a letter of the English alphabet."
	},
	{
		"code": 1228,
		"message": "A server can only have one inbound stream."
	},
	{
		"code": 1229,
		"message": "You cannot archive the default transactional and inbound streams."
	},
	{
		"code": 1230,
		"message": "The 'ID' provided already exists for this server."
	},
	{
		"code": 1231,
		"message": "The 'Description' is too long, it is limited to 1000 characters."
	},
	{
		"code": 1232,
		"message": "You cannot unarchive this message stream anymore."
	},
	{
		"code": 1233,
		"message": "The 'ID' must not start with the 'pm-' prefix."
	},
	{
		"code": 1234,
		"message": "The 'Description' must not contain HTML tags. The characters '<' and '>' are not allowed."
	},
	{
		"code": 1235,
		"message": "The 'MessageStream' provided does not exist on this server."
	},
	{
		"code": 1236,
		"message": "Sending is not supported on the supplied 'MessageStream'."
	},
	{
		"code": 1237,
		"message": "This 'ID' is reserved."
	}
]