diff --git a/src/mail/ngx_mail_handler.c b/src/mail/ngx_mail_handler.c
index 803a247d2..63ae4b003 100644
--- a/src/mail/ngx_mail_handler.c
+++ b/src/mail/ngx_mail_handler.c
@@ -722,11 +722,6 @@ ngx_mail_read_command(ngx_mail_session_t *s, ngx_connection_t *c)
     }
 
     if (n == NGX_AGAIN) {
-        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
-            ngx_mail_session_internal_server_error(s);
-            return NGX_ERROR;
-        }
-
         if (s->buffer->pos == s->buffer->last) {
             return NGX_AGAIN;
         }
diff --git a/src/mail/ngx_mail_imap_handler.c b/src/mail/ngx_mail_imap_handler.c
index e31e4d0c8..5dfdd7601 100644
--- a/src/mail/ngx_mail_imap_handler.c
+++ b/src/mail/ngx_mail_imap_handler.c
@@ -136,7 +136,16 @@ ngx_mail_imap_auth_state(ngx_event_t *rev)
 
     rc = ngx_mail_read_command(s, c);
 
-    if (rc == NGX_AGAIN || rc == NGX_ERROR) {
+    if (rc == NGX_AGAIN) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_session_internal_server_error(s);
+            return;
+        }
+
+        return;
+    }
+
+    if (rc == NGX_ERROR) {
         return;
     }
 
@@ -299,6 +308,11 @@ ngx_mail_imap_auth_state(ngx_event_t *rev)
         }
     }
 
+    if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+        ngx_mail_session_internal_server_error(s);
+        return;
+    }
+
     ngx_mail_send(c->write);
 }
 
diff --git a/src/mail/ngx_mail_pop3_handler.c b/src/mail/ngx_mail_pop3_handler.c
index 019927d3d..edfd98681 100644
--- a/src/mail/ngx_mail_pop3_handler.c
+++ b/src/mail/ngx_mail_pop3_handler.c
@@ -151,7 +151,16 @@ ngx_mail_pop3_auth_state(ngx_event_t *rev)
 
     rc = ngx_mail_read_command(s, c);
 
-    if (rc == NGX_AGAIN || rc == NGX_ERROR) {
+    if (rc == NGX_AGAIN) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_session_internal_server_error(s);
+            return;
+        }
+
+        return;
+    }
+
+    if (rc == NGX_ERROR) {
         return;
     }
 
@@ -281,6 +290,11 @@ ngx_mail_pop3_auth_state(ngx_event_t *rev)
             s->arg_start = s->buffer->start;
         }
 
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_session_internal_server_error(s);
+            return;
+        }
+
         ngx_mail_send(c->write);
     }
 }
diff --git a/src/mail/ngx_mail_proxy_module.c b/src/mail/ngx_mail_proxy_module.c
index 610f54780..299cb2ad2 100644
--- a/src/mail/ngx_mail_proxy_module.c
+++ b/src/mail/ngx_mail_proxy_module.c
@@ -233,6 +233,11 @@ ngx_mail_proxy_pop3_handler(ngx_event_t *rev)
     rc = ngx_mail_proxy_read_response(s, 0);
 
     if (rc == NGX_AGAIN) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
         return;
     }
 
@@ -314,6 +319,11 @@ ngx_mail_proxy_pop3_handler(ngx_event_t *rev)
         return;
     }
 
+    if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
     s->proxy->buffer->pos = s->proxy->buffer->start;
     s->proxy->buffer->last = s->proxy->buffer->start;
 }
@@ -346,6 +356,11 @@ ngx_mail_proxy_imap_handler(ngx_event_t *rev)
     rc = ngx_mail_proxy_read_response(s, s->mail_state);
 
     if (rc == NGX_AGAIN) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
         return;
     }
 
@@ -448,6 +463,11 @@ ngx_mail_proxy_imap_handler(ngx_event_t *rev)
         return;
     }
 
+    if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
     s->proxy->buffer->pos = s->proxy->buffer->start;
     s->proxy->buffer->last = s->proxy->buffer->start;
 }
@@ -482,6 +502,11 @@ ngx_mail_proxy_smtp_handler(ngx_event_t *rev)
     rc = ngx_mail_proxy_read_response(s, s->mail_state);
 
     if (rc == NGX_AGAIN) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_proxy_internal_server_error(s);
+            return;
+        }
+
         return;
     }
 
@@ -763,6 +788,11 @@ ngx_mail_proxy_smtp_handler(ngx_event_t *rev)
         return;
     }
 
+    if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+        ngx_mail_proxy_internal_server_error(s);
+        return;
+    }
+
     s->proxy->buffer->pos = s->proxy->buffer->start;
     s->proxy->buffer->last = s->proxy->buffer->start;
 }
diff --git a/src/mail/ngx_mail_smtp_handler.c b/src/mail/ngx_mail_smtp_handler.c
index dcf658eef..e68ceedfd 100644
--- a/src/mail/ngx_mail_smtp_handler.c
+++ b/src/mail/ngx_mail_smtp_handler.c
@@ -462,7 +462,16 @@ ngx_mail_smtp_auth_state(ngx_event_t *rev)
 
     rc = ngx_mail_read_command(s, c);
 
-    if (rc == NGX_AGAIN || rc == NGX_ERROR) {
+    if (rc == NGX_AGAIN) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_session_internal_server_error(s);
+            return;
+        }
+
+        return;
+    }
+
+    if (rc == NGX_ERROR) {
         return;
     }
 
@@ -574,6 +583,11 @@ ngx_mail_smtp_auth_state(ngx_event_t *rev)
             s->arg_start = s->buffer->pos;
         }
 
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
+            ngx_mail_session_internal_server_error(s);
+            return;
+        }
+
         ngx_mail_send(c->write);
     }
 }