Send error with 2 of 9 accounts

1

"Error sending messages.
Retries exceeded. "

Situation:

  1. Current version: K9 Mail 6.800.
  2. All accounts in the private domains are IMAP-accounts.
  3. Outgoing mail setting (as given by the mail provider):
  • Security: SSL/TLS
  • Port: 465
  • Authentication: Normal password
  • User naam: full account-address
  • Password: checked, checked and double checked.
  • Client certificate: none
    These settings are accepted by the mail server.
  1. K9 Mail is being used for years and never had problems.
  2. There are 14 mail accounts managed, divided in 1 Gmail-account, 1 Hotmail-account and 12 mail accounts on 3 different private domains.
  3. Receiving is going well on all accounts.
  4. With 2 of the 9 accounts in the same private domain is not working and triggers the above-mentioned error message.
  5. This problem didn’t exist when installing the phone and after installing all accounts worked fine. The problem emerged after some time.
  6. When checking or put in again the password, it is every time ok and the password is accepted by the SMTP server.
  7. All accounts in the same domain have the same settings.
  8. I didn’t find any sensible solutions on the internet, or which do solve this problem.
  9. My mail provider and myself, we are very conservative in changing anything. Except normal updates of K9 Mail, nothing is changed for years.

I’m looking for an explanation which can also solve this problem. A general solution can’t explain why there are 2 of the 9 accounts in the same domain which cannot send mail. Also I don’t think the phone has anything to do with it, for all other accounts work just fine. All the accounts have the same settings as noted above.

Which questions do I need to answer to solve this problem?

2

What kind of retrieval method have you set up? Just IMAP pull or also push?

Since Android 11 the amount of app wake-ups as well as the polling frequency have been very limited. You can now only pull in background apps every 15 minutes. Your mail server may have security mechanism in place that to not allow multiple polls from the same IP using different credentials within a short span of time. - Just think that Android keeps back the poll until 15 minutes have passed. Then, it wakes up K-9 and all network interactions occur at the same time. Thus, the server might think an attack has just started from your IP and thus blocks all but the first two connections.

Do you need to poll all accounts? You may rely on push for the important ones and only pull the not so important ones seldomly. If they are more or less unimportant, you could also just set it up to only pull manually. That way, you circumvent the limit completely (active apps and manual connections are not affected by the 15 minute limitation; only applies to background and scheduled activities).

P.S.: Yes, I am aware that your problem is related to sending, but most rate limitations based on security policies apply push, pull the send. Thus, if you are IMAP-blocked, your SMTP connection won’t go through either.

P.P.S.: You could also check your server’s security settings.