diff --git a/ext/imap/php_imap.c b/ext/imap/php_imap.c
index 27ff2058c7a3b..9e9ca677256db 100644
--- a/ext/imap/php_imap.c
+++ b/ext/imap/php_imap.c
@@ -702,10 +702,10 @@ static void php_imap_do_open(INTERNAL_FUNCTION_PARAMETERS, int persistent)
 	zend_long retries = 0, flags = NIL, cl_flags = NIL;
 	MAILSTREAM *imap_stream;
 	pils *imap_le_struct;
-	zval *params = NULL;
+	HashTable *params = NULL;
 	int argc = ZEND_NUM_ARGS();
 
-	if (zend_parse_parameters(argc, "PSS|lla", &mailbox, &user,
+	if (zend_parse_parameters(argc, "PSS|llh", &mailbox, &user,
 		&passwd, &flags, &retries, &params) == FAILURE) {
 		RETURN_THROWS();
 	}
@@ -723,7 +723,7 @@ static void php_imap_do_open(INTERNAL_FUNCTION_PARAMETERS, int persistent)
 	if (params) {
 		zval *disabled_auth_method;
 
-		if ((disabled_auth_method = zend_hash_str_find(Z_ARRVAL_P(params), "DISABLE_AUTHENTICATOR", sizeof("DISABLE_AUTHENTICATOR") - 1)) != NULL) {
+		if ((disabled_auth_method = zend_hash_str_find(params, "DISABLE_AUTHENTICATOR", sizeof("DISABLE_AUTHENTICATOR") - 1)) != NULL) {
 			switch (Z_TYPE_P(disabled_auth_method)) {
 				case IS_STRING:
 					if (Z_STRLEN_P(disabled_auth_method) > 1) {
@@ -866,7 +866,7 @@ PHP_FUNCTION(imap_append)
 	pils *imap_le_struct;
 	STRING st;
 
-	if (zend_parse_parameters(ZEND_NUM_ARGS(), "rSS|SS", &streamind, &folder, &message, &flags, &internal_date) == FAILURE) {
+	if (zend_parse_parameters(ZEND_NUM_ARGS(), "rSS|S!S!", &streamind, &folder, &message, &flags, &internal_date) == FAILURE) {
 		RETURN_THROWS();
 	}
 
@@ -1603,7 +1603,6 @@ PHP_FUNCTION(imap_undelete)
 PHP_FUNCTION(imap_headerinfo)
 {
 	zval *streamind;
-	zend_string *defaulthost = NULL;
 	int argc = ZEND_NUM_ARGS();
 	zend_long msgno, fromlength, subjectlength;
 	pils *imap_le_struct;
@@ -1611,7 +1610,7 @@ PHP_FUNCTION(imap_headerinfo)
 	ENVELOPE *en;
 	char dummy[2000], fulladdress[MAILTMPLEN + 1];
 
-	if (zend_parse_parameters(argc, "rl|llS", &streamind, &msgno, &fromlength, &subjectlength, &defaulthost) == FAILURE) {
+	if (zend_parse_parameters(argc, "rl|ll", &streamind, &msgno, &fromlength, &subjectlength) == FAILURE) {
 		RETURN_THROWS();
 	}
 
@@ -2647,7 +2646,7 @@ PHP_FUNCTION(imap_sort)
 	SEARCHPGM *spg=NIL;
 	int argc = ZEND_NUM_ARGS();
 
-	if (zend_parse_parameters(argc, "rll|lSS", &streamind, &pgm, &rev, &flags, &criteria, &charset) == FAILURE) {
+	if (zend_parse_parameters(argc, "rll|lS!S!", &streamind, &pgm, &rev, &flags, &criteria, &charset) == FAILURE) {
 		RETURN_THROWS();
 	}
 
@@ -2665,7 +2664,7 @@ PHP_FUNCTION(imap_sort)
 			RETURN_FALSE;
 		}
 	}
-	if (argc >= 5) {
+	if (criteria) {
 		search_criteria = estrndup(ZSTR_VAL(criteria), ZSTR_LEN(criteria));
 		spg = mail_criteria(search_criteria);
 		efree(search_criteria);
@@ -2678,7 +2677,7 @@ PHP_FUNCTION(imap_sort)
 	mypgm->function = (short) pgm;
 	mypgm->next = NIL;
 
-	slst = mail_sort(imap_le_struct->imap_stream, (argc == 6 ? ZSTR_VAL(charset) : NIL), spg, mypgm, (argc >= 4 ? flags : NIL));
+	slst = mail_sort(imap_le_struct->imap_stream, (charset ? ZSTR_VAL(charset) : NIL), spg, mypgm, (argc >= 4 ? flags : NIL));
 
 	if (spg && !(flags & SE_FREE)) {
 		mail_free_searchpgm(&spg);
@@ -3411,7 +3410,8 @@ PHP_FUNCTION(imap_mail_compose)
 /* }}} */
 
 /* {{{ _php_imap_mail */
-int _php_imap_mail(char *to, char *subject, char *message, char *headers, char *cc, char *bcc, char* rpath)
+bool _php_imap_mail(zend_string *to, zend_string *subject, zend_string *message, zend_string *headers,
+	zend_string *cc, zend_string *bcc, zend_string* rpath)
 {
 #ifdef PHP_WIN32
 	int tsm_err;
@@ -3420,6 +3420,9 @@ int _php_imap_mail(char *to, char *subject, char *message, char *headers, char *
 	int ret;
 #endif
 
+	ZEND_ASSERT(to && ZSTR_LEN(to) != 0);
+	ZEND_ASSERT(subject && ZSTR_LEN(subject) != 0);
+
 #ifdef PHP_WIN32
 	char *tempMailTo;
 	char *tsm_errmsg = NULL;
@@ -3428,14 +3431,13 @@ int _php_imap_mail(char *to, char *subject, char *message, char *headers, char *
 	size_t offset, bufferLen = 0;
 	size_t bt_len;
 
+	/* Add "To" field's necessary buffer length */
+	bufferLen += ZSTR_LEN(to) + 6;
 	if (headers) {
-		bufferLen += strlen(headers);
-	}
-	if (to) {
-		bufferLen += strlen(to) + 6;
+		bufferLen += ZSTR_LEN(headers);
 	}
 	if (cc) {
-		bufferLen += strlen(cc) + 6;
+		bufferLen += ZSTR_LEN(cc) + 6;
 	}
 
 #define PHP_IMAP_CLEAN	if (bufferTo) efree(bufferTo); if (bufferCc) efree(bufferCc); if (bufferBcc) efree(bufferBcc); if (bufferHeader) efree(bufferHeader);
@@ -3443,41 +3445,41 @@ int _php_imap_mail(char *to, char *subject, char *message, char *headers, char *
 
 	bufferHeader = (char *)safe_emalloc(bufferLen, 1, 1);
 	memset(bufferHeader, 0, bufferLen);
-	if (to && *to) {
-		strlcat(bufferHeader, "To: ", bufferLen + 1);
-		strlcat(bufferHeader, to, bufferLen + 1);
-		strlcat(bufferHeader, "\r\n", bufferLen + 1);
-		tempMailTo = estrdup(to);
-		bt_len = strlen(to);
-		bufferTo = (char *)safe_emalloc(bt_len, 1, 1);
-		bt_len++;
-		offset = 0;
-		addr = NULL;
-		rfc822_parse_adrlist(&addr, tempMailTo, "NO HOST");
-		while (addr) {
-			if (addr->host == NULL || strcmp(addr->host, ERRHOST) == 0) {
-				PHP_IMAP_BAD_DEST;
-			} else {
-				bufferTo = safe_erealloc(bufferTo, bt_len, 1, strlen(addr->mailbox));
-				bt_len += strlen(addr->mailbox);
-				bufferTo = safe_erealloc(bufferTo, bt_len, 1, strlen(addr->host));
-				bt_len += strlen(addr->host);
-				offset += slprintf(bufferTo + offset, bt_len - offset, "%s@%s,", addr->mailbox, addr->host);
-			}
-			addr = addr->next;
-		}
-		efree(tempMailTo);
-		if (offset>0) {
-			bufferTo[offset-1] = 0;
+
+	/* Handle "To" Field */
+	strlcat(bufferHeader, "To: ", bufferLen + 1);
+	strlcat(bufferHeader, ZSTR_VAL(to), bufferLen + 1);
+	strlcat(bufferHeader, "\r\n", bufferLen + 1);
+	tempMailTo = estrdup(ZSTR_VAL(to));
+	bt_len = ZSTR_LEN(to);
+	bufferTo = (char *)safe_emalloc(bt_len, 1, 1);
+	bt_len++;
+	offset = 0;
+	addr = NULL;
+	rfc822_parse_adrlist(&addr, tempMailTo, "NO HOST");
+	while (addr) {
+		if (addr->host == NULL || strcmp(addr->host, ERRHOST) == 0) {
+			PHP_IMAP_BAD_DEST;
+		} else {
+			bufferTo = safe_erealloc(bufferTo, bt_len, 1, strlen(addr->mailbox));
+			bt_len += strlen(addr->mailbox);
+			bufferTo = safe_erealloc(bufferTo, bt_len, 1, strlen(addr->host));
+			bt_len += strlen(addr->host);
+			offset += slprintf(bufferTo + offset, bt_len - offset, "%s@%s,", addr->mailbox, addr->host);
 		}
+		addr = addr->next;
+	}
+	efree(tempMailTo);
+	if (offset>0) {
+		bufferTo[offset-1] = 0;
 	}
 
-	if (cc && *cc) {
+	if (cc && ZSTR_LEN(cc) != 0) {
 		strlcat(bufferHeader, "Cc: ", bufferLen + 1);
-		strlcat(bufferHeader, cc, bufferLen + 1);
+		strlcat(bufferHeader, ZSTR_VAL(cc), bufferLen + 1);
 		strlcat(bufferHeader, "\r\n", bufferLen + 1);
-		tempMailTo = estrdup(cc);
-		bt_len = strlen(cc);
+		tempMailTo = estrdup(ZSTR_VAL(cc));
+		bt_len = ZSTR_LEN(cc);
 		bufferCc = (char *)safe_emalloc(bt_len, 1, 1);
 		bt_len++;
 		offset = 0;
@@ -3501,9 +3503,9 @@ int _php_imap_mail(char *to, char *subject, char *message, char *headers, char *
 		}
 	}
 
-	if (bcc && *bcc) {
-		tempMailTo = estrdup(bcc);
-		bt_len = strlen(bcc);
+	if (bcc && ZSTR_LEN(bcc)) {
+		tempMailTo = estrdup(ZSTR_VAL(bcc));
+		bt_len = ZSTR_LEN(bcc);
 		bufferBcc = (char *)safe_emalloc(bt_len, 1, 1);
 		bt_len++;
 		offset = 0;
@@ -3527,11 +3529,12 @@ int _php_imap_mail(char *to, char *subject, char *message, char *headers, char *
 		}
 	}
 
-	if (headers && *headers) {
-		strlcat(bufferHeader, headers, bufferLen + 1);
+	if (headers && ZSTR_LEN(headers)) {
+		strlcat(bufferHeader, ZSTR_VAL(headers), bufferLen + 1);
 	}
 
-	if (TSendMail(INI_STR("SMTP"), &tsm_err, &tsm_errmsg, bufferHeader, subject, bufferTo, message, bufferCc, bufferBcc, rpath) != SUCCESS) {
+	if (TSendMail(INI_STR("SMTP"), &tsm_err, &tsm_errmsg, bufferHeader, ZSTR_VAL(subject),
+			bufferTo, ZSTR_VAL(message), bufferCc, bufferBcc, ZSTR_VAL(rpath)) != SUCCESS) {
 		if (tsm_errmsg) {
 			php_error_docref(NULL, E_WARNING, "%s", tsm_errmsg);
 			efree(tsm_errmsg);
@@ -3548,15 +3551,15 @@ int _php_imap_mail(char *to, char *subject, char *message, char *headers, char *
 	}
 	sendmail = popen(INI_STR("sendmail_path"), "w");
 	if (sendmail) {
-		if (rpath && rpath[0]) fprintf(sendmail, "From: %s\n", rpath);
-		fprintf(sendmail, "To: %s\n", to);
-		if (cc && cc[0]) fprintf(sendmail, "Cc: %s\n", cc);
-		if (bcc && bcc[0]) fprintf(sendmail, "Bcc: %s\n", bcc);
-		fprintf(sendmail, "Subject: %s\n", subject);
+		if (ZSTR_LEN(rpath) != 0) fprintf(sendmail, "From: %s\n", ZSTR_VAL(rpath));
+		fprintf(sendmail, "To: %s\n", ZSTR_VAL(to));
+		if (ZSTR_LEN(cc) != 0) fprintf(sendmail, "Cc: %s\n", ZSTR_VAL(cc));
+		if (ZSTR_LEN(bcc) != 0) fprintf(sendmail, "Bcc: %s\n", ZSTR_VAL(bcc));
+		fprintf(sendmail, "Subject: %s\n", ZSTR_VAL(subject));
 		if (headers != NULL) {
-			fprintf(sendmail, "%s\n", headers);
+			fprintf(sendmail, "%s\n", ZSTR_VAL(headers));
 		}
-		fprintf(sendmail, "\n%s\n", message);
+		fprintf(sendmail, "\n%s\n", ZSTR_VAL(message));
 		ret = pclose(sendmail);
 
 		return ret != -1;
@@ -3575,7 +3578,7 @@ PHP_FUNCTION(imap_mail)
 	zend_string *to=NULL, *message=NULL, *headers=NULL, *subject=NULL, *cc=NULL, *bcc=NULL, *rpath=NULL;
 	int argc = ZEND_NUM_ARGS();
 
-	if (zend_parse_parameters(argc, "SSS|SSSS", &to, &subject, &message,
+	if (zend_parse_parameters(argc, "PPP|P!P!P!P!", &to, &subject, &message,
 		&headers, &cc, &bcc, &rpath) == FAILURE) {
 		RETURN_THROWS();
 	}
@@ -3598,8 +3601,7 @@ PHP_FUNCTION(imap_mail)
 		php_error_docref(NULL, E_WARNING, "No message string in mail command");
 	}
 
-	if (_php_imap_mail(ZSTR_VAL(to), ZSTR_VAL(subject), ZSTR_VAL(message), headers?ZSTR_VAL(headers):NULL, cc?ZSTR_VAL(cc):NULL,
-			bcc?ZSTR_VAL(bcc):NULL, rpath?ZSTR_VAL(rpath):NULL)) {
+	if (_php_imap_mail(to, subject, message, headers, cc, bcc, rpath)) {
 		RETURN_TRUE;
 	} else {
 		RETURN_FALSE;
diff --git a/ext/imap/php_imap.stub.php b/ext/imap/php_imap.stub.php
index 9d2e1082c1a7c..0a7adc2736977 100644
--- a/ext/imap/php_imap.stub.php
+++ b/ext/imap/php_imap.stub.php
@@ -5,7 +5,7 @@
 /**
  * @return resource|false
  */
-function imap_open(string $mailbox, string $user, string $password, int $options = 0, int $n_retries = 0, array $params = UNKNOWN) {}
+function imap_open(string $mailbox, string $user, string $password, int $options = 0, int $n_retries = 0, array $params = []) {}
 
 /**
  * @param resource $stream_id
@@ -27,13 +27,7 @@ function imap_num_recent($stream_id): int|false {}
 function imap_headers($stream_id): array|false {}
 
 /** @param resource $stream_id */
-function imap_headerinfo($stream_id, int $msg_no, int $from_length = 0, int $subject_length = 0, string $default_host = UNKNOWN): stdClass|false {}
-
-/**
- * @param resource $stream_id
- * @alias imap_headerinfo
- */
-function imap_header($stream_id, int $msg_no, int $from_length = 0, int $subject_length = 0, string $default_host = UNKNOWN): stdClass|false {}
+function imap_headerinfo($stream_id, int $msg_no, int $from_length = 0, int $subject_length = 0): stdClass|false {}
 
 function imap_rfc822_parse_headers(string $headers, string $default_host = "UNKNOWN"): stdClass {}
 
@@ -148,7 +142,7 @@ function imap_subscribe($stream_id, string $mailbox): bool {}
 function imap_unsubscribe($stream_id, string $mailbox): bool {}
 
 /** @param resource $stream_id */
-function imap_append($stream_id, string $folder, string $message, string $options = UNKNOWN, string $internal_date = UNKNOWN): bool {}
+function imap_append($stream_id, string $folder, string $message, ?string $options = null, ?string $internal_date = null): bool {}
 
 /** @param resource $stream_id */
 function imap_ping($stream_id): bool {}
@@ -180,7 +174,7 @@ function imap_setflag_full($stream_id, string $sequence, string $flag, int $opti
 function imap_clearflag_full($stream_id, string $sequence, string $flag, int $options = 0): bool {}
 
 /** @param resource $stream_id */
-function imap_sort($stream_id, int $criteria, int $reverse, int $options = 0, string $search_criteria = UNKNOWN, string $charset = UNKNOWN): array|false {}
+function imap_sort($stream_id, int $criteria, int $reverse, int $options = 0, ?string $search_criteria = null, ?string $charset = null): array|false {}
 
 /** @param resource $stream_id */
 function imap_uid($stream_id, int $msg_no): int|false {}
@@ -258,4 +252,4 @@ function imap_setacl($stream_id, string $mailbox, string $id, string $rights): b
 function imap_getacl($stream_id, string $mailbox): array|false {}
 #endif
 
-function imap_mail(string $to, string $subject, string $message, string $additional_headers = UNKNOWN, string $cc = UNKNOWN, string $bcc = UNKNOWN, string $rpath = UNKNOWN): bool {}
+function imap_mail(string $to, string $subject, string $message, ?string $additional_headers = null, ?string $cc = null, ?string $bcc = null, ?string $rpath = null): bool {}
diff --git a/ext/imap/php_imap_arginfo.h b/ext/imap/php_imap_arginfo.h
index 69fe25e4d0f4c..ffb60a034f890 100644
--- a/ext/imap/php_imap_arginfo.h
+++ b/ext/imap/php_imap_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 4991f82d78672ab23044864fa6dd75851952965c */
+ * Stub hash: e501d6869d721ad720a1a7c8b597b96e9591d5ed */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_imap_open, 0, 0, 3)
 	ZEND_ARG_TYPE_INFO(0, mailbox, IS_STRING, 0)
@@ -7,7 +7,7 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_imap_open, 0, 0, 3)
 	ZEND_ARG_TYPE_INFO(0, password, IS_STRING, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, options, IS_LONG, 0, "0")
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, n_retries, IS_LONG, 0, "0")
-	ZEND_ARG_TYPE_INFO(0, params, IS_ARRAY, 0)
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, params, IS_ARRAY, 0, "[]")
 ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_imap_reopen, 0, 2, _IS_BOOL, 0)
@@ -37,11 +37,8 @@ ZEND_BEGIN_ARG_WITH_RETURN_OBJ_TYPE_MASK_EX(arginfo_imap_headerinfo, 0, 2, stdCl
 	ZEND_ARG_TYPE_INFO(0, msg_no, IS_LONG, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, from_length, IS_LONG, 0, "0")
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, subject_length, IS_LONG, 0, "0")
-	ZEND_ARG_TYPE_INFO(0, default_host, IS_STRING, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_imap_header arginfo_imap_headerinfo
-
 ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_imap_rfc822_parse_headers, 0, 1, stdClass, 0)
 	ZEND_ARG_TYPE_INFO(0, headers, IS_STRING, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, default_host, IS_STRING, 0, "\"UNKNOWN\"")
@@ -173,8 +170,8 @@ ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_imap_append, 0, 3, _IS_BOOL, 0)
 	ZEND_ARG_INFO(0, stream_id)
 	ZEND_ARG_TYPE_INFO(0, folder, IS_STRING, 0)
 	ZEND_ARG_TYPE_INFO(0, message, IS_STRING, 0)
-	ZEND_ARG_TYPE_INFO(0, options, IS_STRING, 0)
-	ZEND_ARG_TYPE_INFO(0, internal_date, IS_STRING, 0)
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, options, IS_STRING, 1, "null")
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, internal_date, IS_STRING, 1, "null")
 ZEND_END_ARG_INFO()
 
 #define arginfo_imap_ping arginfo_imap_expunge
@@ -217,8 +214,8 @@ ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(arginfo_imap_sort, 0, 3, MAY_BE_ARRAY|MA
 	ZEND_ARG_TYPE_INFO(0, criteria, IS_LONG, 0)
 	ZEND_ARG_TYPE_INFO(0, reverse, IS_LONG, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, options, IS_LONG, 0, "0")
-	ZEND_ARG_TYPE_INFO(0, search_criteria, IS_STRING, 0)
-	ZEND_ARG_TYPE_INFO(0, charset, IS_STRING, 0)
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, search_criteria, IS_STRING, 1, "null")
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, charset, IS_STRING, 1, "null")
 ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(arginfo_imap_uid, 0, 2, MAY_BE_LONG|MAY_BE_FALSE)
@@ -342,10 +339,10 @@ ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_imap_mail, 0, 3, _IS_BOOL, 0)
 	ZEND_ARG_TYPE_INFO(0, to, IS_STRING, 0)
 	ZEND_ARG_TYPE_INFO(0, subject, IS_STRING, 0)
 	ZEND_ARG_TYPE_INFO(0, message, IS_STRING, 0)
-	ZEND_ARG_TYPE_INFO(0, additional_headers, IS_STRING, 0)
-	ZEND_ARG_TYPE_INFO(0, cc, IS_STRING, 0)
-	ZEND_ARG_TYPE_INFO(0, bcc, IS_STRING, 0)
-	ZEND_ARG_TYPE_INFO(0, rpath, IS_STRING, 0)
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, additional_headers, IS_STRING, 1, "null")
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, cc, IS_STRING, 1, "null")
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, bcc, IS_STRING, 1, "null")
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, rpath, IS_STRING, 1, "null")
 ZEND_END_ARG_INFO()
 
 
@@ -440,7 +437,6 @@ static const zend_function_entry ext_functions[] = {
 	ZEND_FE(imap_num_recent, arginfo_imap_num_recent)
 	ZEND_FE(imap_headers, arginfo_imap_headers)
 	ZEND_FE(imap_headerinfo, arginfo_imap_headerinfo)
-	ZEND_FALIAS(imap_header, imap_headerinfo, arginfo_imap_header)
 	ZEND_FE(imap_rfc822_parse_headers, arginfo_imap_rfc822_parse_headers)
 	ZEND_FE(imap_rfc822_write_address, arginfo_imap_rfc822_write_address)
 	ZEND_FE(imap_rfc822_parse_adrlist, arginfo_imap_rfc822_parse_adrlist)