Ethernet chip lan8720

[Over-IQ]

Hello.
I really liked your email library for esp32. Is there support for ethernet chip lan8720? I'm trying to send an email through it, but get the message "ETH Disconnected
" and crashing esp32.

[mobizt]

You should modify LAN8720 module to use external clock that outputs from ESP32 GPIO.
See the image in the example folder.
https://github.com/mobizt/ESP-Mail-Client/tree/master/examples/SMTP/Ethernet/ESP32/Send_Text

[Over-IQ]

The ethernet works fine up to the point where I try to send an email. After that, ethernet stops working completely. If you use wifi connection everything is ok.
I updated SDK from 1.0.6 to 2.0.6. Esp32 stopped crashing, but ethernet still disconnects.

Connecting to SMTP server...
> C: Wait for NTP server time synching
ETH Disconnected
Error, unable to connect to server
Error, connection closed
Error sending Email, connection closed

[mobizt]

The problem is on your ethernet module or router which ethernet should be connected and available all the time.

[Over-IQ]

There is also a web server. Until the email is sent. Maybe some timeout expires?

[mobizt]

I don't know. The error is from WiFi event callback

ESP-Mail-Client/examples/SMTP/Ethernet/ESP32/Send_Text/Send_Text.ino

Line 138 in ac39ffe

Serial.println("ETH Disconnected");

The library can't control the network interface. The ethernet should be initialized by user. Library checks for its link status from calling ETH.linkUp(), no special code required for Ethernet as it is supported natively by core.

[Over-IQ]

I tried your example. The error is present. I tried on two different boards. Clocking 8720 comes from esp32. Perhaps this is the reason? Could the email library be so heavy on the CPU that the 8720 would stop clocking for a while?
ETH Started
ETH Connected
ETH MAC: 98:F4:AB:16:59:CF, IPv4: 192.168.21.215, FULL_DUPLEX, 100Mbps
Connecting to SMTP server...
> C: ESP Mail Client v2.7.10
> C: Wait for NTP server time synching
ETH Disconnected
> C: Connect to SMTP server
> C: Host > smtp.mail.ru
> C: Port > 465
> C: cleaning SSL connection
> C: seeding the random number generator
> C: setting up the SSL/TLS structure
! W: Skipping SSL Verification. INSECURE!
> C: setting hostname for TLS session
> C: perform the SSL/TLS handshake
! E: ERROR - Generic error
> C: cleaning SSL connection
Error, unable to connect to server
> E: unable to connect to server
Error, connection closed
> E: connection closed
Error sending Email, connection closed

[Over-IQ]

I found what was the problem. I disabled those lines and it worked.
File ESP_Mail_SMTP.h
if (!_customCmdResCallback && (_sesson_cfg->time.ntp_server.length() > 0 || validTime))
{
s = esp_mail_str_355;
if (!_customCmdResCallback)
esp_mail_debug_print(s.c_str(), true);
//MailClient.setTime(_sesson_cfg->time.gmt_offset, _sesson_cfg->time.day_light_offset, _sesson_cfg->time.ntp_server.c_str(), _sesson_cfg->time.timezone_env_string.c_str(), _sesson_cfg->time.timezone_file.c_str(), true);

//if (!MailClient.Time.clockReady())
// MailClient.errorStatusCB(this, MAIL_CLIENT_ERROR_NTP_TIME_SYNC_TIMED_OUT);
}

[mobizt]

The code you commented related to NTP time sync by calling core function configTime.
I will investigate this issue why ethernet affected by configTime and may use UDP client for time synching instead.

[mobizt]

You should set your device time manually before calling smtp.connect because the valid time is needed to set the date/time header otherwise your message will not be valid for RFC guideline which valid Date: header is the required field and your message may be considered as spam or junk message by mail server. That's why the library is trying to sync the time first (if the time was not set) when sending email.