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Buffer is full while sending email via IPsec VPN

I'm facing exactly the same error like the one described here -


The difference is that I have the same ‘reply-to’ and ‘username’ addresses in configuration.


config system email-server
set reply-to ""
set server ""
set port 587
set source-ip IPofTheDeviceBehindIPsecTunnel
set authenticate enable
set username ""
set password sdfsdfsdfsdfsdfdsfsdf(formatted)
set security starttls



The fortigate device1 is connected with another fortigate device2 via IPsec Tunnel (dns is working fine). This particular fortigate device1 does not have direct access to WAN, all traffic goes via the tunnel and device2 has connection with Internet. That's why i have specified source-ip of the device2 within email-server config.


Any ideas what is wrong? I want to be informed via email from device2 directly.


Hello @roleit ,


Hope you are doing well.

Can you try using the default Fortinet email server setting and test if it is working or not rather than ?


article reference:


-For testing remove source-ip wan address for now 

You can unset the source ip using the below steps :

 config system email-server

 unset source-ip



Please run the debugs once again and verify if seeing the same buffer error.


diag debug reset

diag debug console timestamp enable

diag debug app alertemail -1

diag debug enable

diag debug disable   ----- to stop debugs

diag debug reset



I have changed settings to default and unset source-ip.


Below fresh logs:


2023-08-11 14:07:26 mail_info:  ""

2023-08-11 14:07:26 mail_info:


        user name:device2name

2023-08-11 14:07:26 to[0]

2023-08-11 14:07:26 <==_init_mail_info

2023-08-11 14:07:26 create session

2023-08-11 14:07:26 resolve to 1 IP

2023-08-11 14:07:26 ==> send mail

2023-08-11 14:07:26 connecting to port 465

2023-08-11 14:07:26 send mail 0x8f6b650 session 0x8f301a0

2023-08-11 14:08:30 failed to connect

2023-08-11 14:08:30 session_io_event: creating ssl structure for session 0x8f301a0

2023-08-11 14:08:30 create_ssl: 0x7fb4968000

2023-08-11 14:08:30 error in SSL_connect (null)

2023-08-11 14:08:30 _session_on_destroy

2023-08-11 14:08:30 <== send mail failed, m = 0x8f6b650 s = 0x8f301a0


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