upgrade deps; rewrite smtp session

vendor/github.com/jhillyerd/enmime/parser.go

@@ -1,10 +1,31 @@
 package enmime
 
+// ReadPartErrorPolicy allows to recover the buffer (or not) on an error when reading a Part content.
+//
+// See AllowCorruptTextPartErrorPolicy for usage.
+type ReadPartErrorPolicy func(*Part, error) bool
+
+// AllowCorruptTextPartErrorPolicy recovers partial content from base64.CorruptInputError when content type is text/plain or text/html.
+func AllowCorruptTextPartErrorPolicy(p *Part, err error) bool {
+	if IsBase64CorruptInputError(err) && (p.ContentType == ctTextHTML || p.ContentType == ctTextPlain) {
+		return true
+	}
+	return false
+}
+
+// CustomParseMediaType parses media type. See ParseMediaType for more details
+type CustomParseMediaType func(ctype string) (mtype string, params map[string]string, invalidParams []string, err error)
+
 // Parser parses MIME.
 // Default parser is a valid one.
 type Parser struct {
-	skipMalformedParts              bool
+	maxStoredPartErrors             *int // TODO: Pointer until global var removed.
 	multipartWOBoundaryAsSinglePart bool
+	readPartErrorPolicy             ReadPartErrorPolicy
+	skipMalformedParts              bool
+	rawContent                      bool
+	customParseMediaType            CustomParseMediaType
+	stripMediaTypeInvalidCharacters bool
 }
 
 // defaultParser is a Parser with default configuration.