SMTP return code upon message sending completion should be checked

[yuliu]

Community thread: https://community.mybb.com/thread-224905-post-1349025.html#pid1349025

Relevant code that will trigger errors:

mybb/sendthread.php

Line 215 in 4c5451a

my_mail($mybb->input['email'], $mybb->input['subject'], $message, $from, "", "", false, "text", "", $mybb->input['fromemail']);

./sendthread.php - send thread to a friend:
$from: $mybb->input['fromemail'] from $mybb->user['email'] for logged in user
$return_email: $mybb->input['fromemail'] from $mybb->user['email'] for logged in user
The mail will be sent from [b]a user-specified email address[/b] which confronts mail SMTP service's requirement, like Zoho's requiring from is the same as sending account's email address.

Still for Zoho, setting a different Return Email other than SMTP username will result in no mail delivered and MyBB frequently set Return Email as from: field if it's empty.

So in the above circumstances, Zoho's SMTP authentication will pass but when the full message is sent with a final ending ., the server will probably return a 553 code 553 Relaying disallowed as xxx@yyy.zzz, which MyBB doesn't take care of.

[yuliu]

Oh by the way, the underlying reason that prevents mail's delivering is MyBB's wildly setting from: (and return-path:).

Ah just find it a duplicate of #2644. Should we fix it? @euantorano

According to https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol#SMTP_transport_example , a final 250 upon message acceptance should be issued from server and we should check.

[euantorano]

Yeah, I think it’s worth fixing if the fix is simple.