On my todo list: experiment with having multiple sendmail queue directories under /var/spool/mqueue
Posted by jpluimers on 2018/09/27
Right now my sendmail configuration handling my domains have one queue directory /var/spool/mqueue which means that each round of the queue processing handles all the outgoing mail in succession.
This is getting less OK because of the increased mail volume over time both on mail that gets in and needs to be forwarded and mail that needs to be bounced for various reasons like SPAM.
So below are some links helping me to sort out various things including having multiple queues (as then each round can handle each queue in parallel).
The default sendmail configuration is one mail queue and I hope to find out for what reason that is.
- [Archive.is] Sendmail queue runner query – with deep queues starting from scratch… – Google Groups
- [WayBack] Sendmail Multiple Queues – MDLog:/sysadmin
- [WayBack] 11.4 Queue Groups (V8.12 and Above)
- [WayBack] sendmail 8.10.0
- [WayBack] 6.1 Handle Deep Queues
- [WayBack] SingleThreadDelivery – Set single-threaded delivery (V8.8 and later)
- [WayBack] QueueSortOrder; How to presort the queue (V8.7 and later)
- [WayBack] NORMAL OPERATIONS
- [WayBack] Howto – Sendmail – MailScanner
Background info:
- [WayBack] Extended SMTP – Wikipedia
- [WayBack] RFC 1869 – SMTP Service Extensions
- [WayBack] Simple Mail Transfer Protocol – Wikipedia
SPAM on my systems cause these very frequently:
- SMTP 421 response codes on domains getting too many bounces (usually in the form 421 “out of connection slots”). These immediately end the SMTP session.
- [WayBack] RFC 2821 – Simple Mail Transfer Protocol: Reply Code Severities and Theory
- [Archive.is] Email error 421 – Knowledgebase – eJapan Office – Intermediation LLC
- [WayBack] SMTP reply codes
- [WayBack] SMTP error messages and reply codes | smtp mail server
- None of the bulk email services mentioned at [WayBack] php – What to do in case of SMTP 421 error? – Stack Overflow do that.
- Timeouts of SPAM domains not accepting incoming SMTP
I want to eventually split those out in separate queues separate of the main mail processing.
This probably requires some scripting instead of just sendmail configuration changes.
And some of my past sendmail posts for easier reference:
- [WayBack] a few notes on sendmail and re-trying deferred messages
- [WayBack] Flush deferred messages in sendmail queue :: Stephan Paukner :: syslog
–jeroen
The Wiert Corner - irregular stream of stuff 
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