Email messages not delivering
How it looks:
Messages accepted by server (from your email app via SMTP or from Mautic) but not delivered to external mailboxes.
There are two information sources for definitions reason of not delivery
- bounce reports in mailbox which used as <FROM> address
- MTA log files
Bounce reports
Your mailings can be bounced on some steps
- Flynet's outgoing SMTP quality filter gateways
- External SMTP servers (like gmail.com, yahoo.com)
In all of these cases bounce report will be delivered back to mailbox from which message was originated.
If you use your own mailing software with SMTP credential only - it will be mailbox from credentials. (admin@yourdomain.com)
If you use Mautic - it will be mailbox bounce@yourdomain.com
For check bounces go to 'VPS hosting' page -> select string with your server -> press on 'Instructions' button on top. On new opened page 'Virtual server activation' find chapter 'SMTP credentials & webmail'. This what you need:
SMTP username: admin@yourdomain.com
SMTP password: somepassword
Webmail RoundCube: http://webmail.yourdomain.com
Go to link 'Webmail RoundCube' from this chapter and fill login (admin@yourdomian.com or mautic@yourdomain.com) and password from this chapter. Pay attention password for mailbox mautic@ is same as admin@ by default)
If your dont know what mailbox uses for sending you can see one in exim stats:
'VPS hosting' page -> select string with your server -> press on 'Instructions' button on top. On new opened page 'Virtual server activation' find chapter 'Hestia LAMP control panel'.
Login in Hestia control panel -> press on gear icon on top -> press on 'Task Monitor' button -> press on 'View Advanced Details' button -> press on 'Mail' tab on top -> find 'Top 50 local senders by message count' chapter (you can use Ctrl+F for find this substring).
Spam alert
In logged Webmail RoundCube webmail interface go to Mail -> Inbox -> find last message with subject 'SPAM alert' -> open it
See at string:
Score: X.XX (must be lower 2.00)
Symbols:
If 'Score' greater then 2.00 your messages will be bounced.
Score calculated from sum of each 'Symbol' scores.
Score of each 'Symbol' string placed in rounded brackets.
'Symbols' are quality metrics of your messages. If your message will be pretty good - this message will be released by our SMTP gateways and will be placed in "Inbox" folder in recipient mailbox (not SPAM folder.
If your message is dirty bad - this message will be filtered by our SMTP gateways and you will be receive this bounce message (Spam alert).
This way helps us to protect reputation of our IP's and yours domains.
You can enfluence on 'Score' (reduce) metric by re-writing your email template (body, subject, headers) or adjusting domain settings (DKIM, SPF, DNS RBL delisting).
When 'Score' will be lower then 2.00 - your mailings will be released.
Start from 'Symbols' with max scores, they have max influence.
Sometime 'Symbols' can has only one string with '0.00' score. (for example reject_known_bad_recipient_address). This means that this rule alone is enough to block sending.
list of more often 'Symbols' with ways to solution
Mail delivery failed: returning message to sender
Sometimes good pretty emails can be bounced by reasons:
- mailbox is disabled or not existent
- specific restrictions of recipient server (rate limits)
Similar issues needs individual solution based on reject reason.
No bounces but mailings not going
This may be coursed by delaying messages on your server (soft bounces). In this case no bounces generates and messages stays in server queue and can be deliverd later.
For start check exim queue:
'VPS hosting' page -> select string with your server -> press on 'Instructions' button on top. On new opened page 'Virtual server activation' find chapter 'Hestia LAMP control panel'.
Login in Hestia control panel -> press on gear icon on top -> press on 'Task Monitor' button -> scroll to 'Exim Usage' graph -> see on 'Curent' value on graph. This is count of messages in Exim MTA queue now.
If this value not 0 - some of your messages defferred. Pay attention, this graph updated once per 5 minutes.
For immideately show queue status press on 'View Advanced Details' button -> press on 'Mail' tab on top -> find 'Exim queue status' chapter (on top).
You can see reason of deferring via ssh:
'VPS hosting' page -> select string with your server -> press on 'Instructions' button on top. On new opened page 'Virtual server activation' find chapter 'Server information'.
Connect via ssh with root password and run:
tail -f /var/log/exim4/mainlog | grep '=='
where '==' is deferring sign in exim logs. Example of output:
2021-10-04 17:34:55 1mXGcJ-0004Bc-88 == mailbox@yahoo.com R=dnslookup T=remote_smtp defer (-46) H=mta6.am0.yahoodns.net [98.136.96.91]: SMTP error from remote mail server after end of data: 451 4.7.1 Sender domain temporary blocked. Too many bounces. (client_address=193.33.87.187 server_name=rsp105.mxflnt.com)
Reason in curren case is 'Sender domain temporary blocked. Too many bounces.'