log all smtp connection errors

go.mod

@@ -20,7 +20,7 @@ require (
 	gitlab.com/etke.cc/go/logger v1.1.0
 	gitlab.com/etke.cc/go/mxidwc v1.0.0
 	gitlab.com/etke.cc/go/secgen v1.1.1
-	gitlab.com/etke.cc/go/trysmtp v1.1.1
+	gitlab.com/etke.cc/go/trysmtp v1.1.2
 	gitlab.com/etke.cc/go/validator v1.0.6
 	gitlab.com/etke.cc/linkpearl v0.0.0-20221116205701-65547c5608e6
 	maunium.net/go/mautrix v0.12.3

go.sum

@@ -103,8 +103,8 @@ gitlab.com/etke.cc/go/mxidwc v1.0.0 h1:6EAlJXvs3nU4RaMegYq6iFlyVvLw7JZYnZmNCGMYQ
 gitlab.com/etke.cc/go/mxidwc v1.0.0/go.mod h1:E/0kh45SAN9+ntTG0cwkAEKdaPxzvxVmnjwivm9nmz8=
 gitlab.com/etke.cc/go/secgen v1.1.1 h1:RmKOki725HIhWJHzPtAc9X4YvBneczndchpMgoDkE8w=
 gitlab.com/etke.cc/go/secgen v1.1.1/go.mod h1:3pJqRGeWApzx7qXjABqz2o2SMCNpKSZao/gXVdasqE8=
-gitlab.com/etke.cc/go/trysmtp v1.1.1 h1:4mbkfsfipidG2eO8/zSozJ78Vv/lRAcdznvjK0fMVuo=
-gitlab.com/etke.cc/go/trysmtp v1.1.1/go.mod h1:lOO7tTdAE0a3ETV3wN3GJ7I1Tqewu7YTpPWaOmTteV0=
+gitlab.com/etke.cc/go/trysmtp v1.1.2 h1:Jg+J/zgx77wqJ9J5L5dlKFoQLka6yYTXa2wf+GNhjnQ=
+gitlab.com/etke.cc/go/trysmtp v1.1.2/go.mod h1:lOO7tTdAE0a3ETV3wN3GJ7I1Tqewu7YTpPWaOmTteV0=
 gitlab.com/etke.cc/go/validator v1.0.6 h1:w0Muxf9Pqw7xvF7NaaswE6d7r9U3nB2t2l5PnFMrecQ=
 gitlab.com/etke.cc/go/validator v1.0.6/go.mod h1:Id0SxRj0J3IPhiKlj0w1plxVLZfHlkwipn7HfRZsDts=
 gitlab.com/etke.cc/linkpearl v0.0.0-20221116205701-65547c5608e6 h1:+HDT2/bx3Hug++aeDE/PaoRRcnKdYzEm6i2RlOAzPXo=

smtp/server.go

@@ -93,10 +93,13 @@ func (m *mailServer) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session,
 func (m *mailServer) SendEmail(from, to, data string) error {
 	m.log.Debug("Sending email from %s to %s", from, to)
 	conn, err := trysmtp.Connect(from, to)
-	if err != nil {
+	if conn == nil {
 		m.log.Error("cannot connect to SMTP server of %s: %v", to, err)
 		return err
 	}
+	if err != nil {
+		m.log.Warn("connection to the SMTP server of %s returned the following non-fatal error(-s): %v", err)
+	}
 	defer conn.Close()
 
 	var w io.WriteCloser

vendor/gitlab.com/etke.cc/go/trysmtp/client.go

@@ -12,15 +12,16 @@ import (
 var SMTPAddrs = []string{":25", ":587", ":465"}
 
 // Connect to SMTP server and call MAIL and RCPT commands
+// NOTE: check if client is not nil, because it can return non-fatal errors with initialized client
 func Connect(from, to string) (*smtp.Client, error) {
 	localname := strings.SplitN(from, "@", 2)[1]
 	hostname := strings.SplitN(to, "@", 2)[1]
-	client, err := initClient(localname, hostname)
-	if err != nil {
-		return nil, err
+	client, cerr := initClient(localname, hostname)
+	if client == nil {
+		return nil, cerr
 	}
 
-	err = client.Mail(from)
+	err := client.Mail(from)
 	if err != nil {
 		client.Close()
 		return nil, err
@@ -32,7 +33,7 @@ func Connect(from, to string) (*smtp.Client, error) {
 		return nil, err
 	}
 
-	return client, nil
+	return client, cerr
 }
 
 func unwrapErrors(errs []error) error {

vendor/modules.txt

@@ -134,7 +134,7 @@ gitlab.com/etke.cc/go/mxidwc
 # gitlab.com/etke.cc/go/secgen v1.1.1
 ## explicit; go 1.19
 gitlab.com/etke.cc/go/secgen
-# gitlab.com/etke.cc/go/trysmtp v1.1.1
+# gitlab.com/etke.cc/go/trysmtp v1.1.2
 ## explicit; go 1.17
 gitlab.com/etke.cc/go/trysmtp
 # gitlab.com/etke.cc/go/validator v1.0.6