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Incoming (IMAP) emails intermittently delayed

John_B
Hooked
Posts: 8
Thanks: 1
Registered: ‎26-10-2019

Incoming (IMAP) emails intermittently delayed

Dear Forum, I am a long-term user of Plusnet Broadband and Email, all of which has worked well.

However in past month I have intermittently experienced a "delay" problem with incoming emails. Some days it is fine;on other days it is necessary to go to webmail because delay is many hours.

Microsoft office 2016.

IMAP Incoming server:  imap.plus.net : port143   No encryption

SMTP Outgoing server:  relay.plus.net ; port 25   No encryption

Polling interval to synchronise PC with servers  3 mins (background mode)

It is sometimes possible to "wake up" the incoming mail process by sending a brief loopback "tester" email to my own address from the same Plusnet acoount (i.e same PC) , in which case a batch of emails magically appears. These emails will have "received timestamps" spread over the silent period. This does not always work, It does seem that maybe the IMAP server is waiting until the backlog has got big enough to trigger delivery to my PC.

All comments welcome

John_B

7 REPLIES 7
Townman
Superuser
Superuser
Posts: 16,895
Thanks: 6,995
Fixes: 67
Registered: ‎22-08-2007

Re: Incoming (IMAP) emails intermittently delayed

Hi John,

It could be many things, including a problematic link, or issues with another mailbox being accessed by Outlook.  The poll interval of 3 minutes might not be overly helpful, for in some circumstances, that might not be long enough to allow one sync cycle to complete.

Some points to not - encryption can (ought to) be used...

  • IMAP port 993 encryption SSL/TLS
  • SMTP port 587 encryption STARTTLS (note port 25 should NOT be used for message SUBMISSION)

Are there other email accounts configured in OUTLOOK 2016?  I have an outlook.com one configured and I find that access to that can be flaky and can cause delays in syncing my Plusnet mailboxes ... and then as you note, a bunch arrive together.  Ironically as I write this (clearly with good connectivity to the internet) my OUTLOOK 2016 is reporting connectivity problems - whilst happily syncing my Plusnet mailboxes.

...now hours later everything is simply fine.

John_B
Hooked
Posts: 8
Thanks: 1
Registered: ‎26-10-2019

Re: Incoming (IMAP) emails intermittently delayed

Hi Townman,

Many thanks for your comments. I have updated server settings to

IMAP Incoming server:  imap.plus.net : port 993   SSL/TLS

SMTP Outgoing server:  relay.plus.net ; port 587   STARTTLS

I would have set these based on  old Plusnet guidance docs. possibly a decade old!

I will extend the sync timer to 5 Mins, although I have never seen a successful sync take longer than a minute or so.

There is only one "Email account" (The plusnet account) in the PC's Outlook 2016 "configuration" data.

As far as I can tell the Plusnet Broad band is working well on PC Web browsing, and "Netflix/iPlayer" TV streaming. Downlink about 15Mb/s. Uplink 0.8Mb/s Ping 30ms.

Lets see how that goes.

Today has been a bad day, because only one batch of about 10  incoming emails early this morning, which was  immediately after I had sent in a loopback test message containing a 3MB picture. I am sceptical it was co-incidence! The other emails were small (size <50KB) and it would seem waiting to be sent when there worth doing!

Best wishes

John_B

John_B
Hooked
Posts: 8
Thanks: 1
Registered: ‎26-10-2019

Re: Incoming (IMAP) emails intermittently delayed

Hi Townman,

I hope this is now solved. Many thanks for your assistance.

I also used the "Email Account Repair" function in Outlook 2016 later on Saturday. Performance of  receipt of emails is still a bit variable, but far more emails are being delivered at or close to the "Received" timestamp within the message.

Vast improvement. Much appreciated your guidance for updating Port numbers and Encryption settings.

John_B

Townman
Superuser
Superuser
Posts: 16,895
Thanks: 6,995
Fixes: 67
Registered: ‎22-08-2007

Re: Incoming (IMAP) emails intermittently delayed

"which was  immediately after I had sent in a loopback test message containing a 3MB picture"

Ahh!!

Emails with sizable attachments can cause performance issues exactly as you describe!  Though it works, email is not a good method of sharing pictures - better to use cloud base storage (if you have a subscription for OUTLOOK 2016 you will have One Drive) and to share a link to the files.

John_B
Hooked
Posts: 8
Thanks: 1
Registered: ‎26-10-2019

Re: Incoming (IMAP) emails intermittently delayed

Hi Townman.

The use and value of cloud for sharing large files is not disputed.

However sending an email to myself is apparently the only reasonably effective tool I have to force the delivery of emails which are sitting on the Plusnet server (as judged by their "received" timestamps). I have found that an email with a 3MB attachment is much more effective in encouraging the "IMAP" server to send me my delayed mails than a 10KB loopback email.

Regrettably the base problem has resurfaced this afternoon with my having just received a batch of eight emails including your post/notification which  was delayed by about 6 hours (from 12.17).

All more thoughts on the original issue?...anyone?

Townman
Superuser
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Posts: 16,895
Thanks: 6,995
Fixes: 67
Registered: ‎22-08-2007

Re: Incoming (IMAP) emails intermittently delayed

"effective in encouraging the "IMAP" server to send me my delayed mails"

That needs to be dismissed - this is not a "push" dialogue but a "pull" action.  The IMAP serve does not send as in force and unsolicited transfer, the client requests the content.  This this is more probably a client performance issue that an IMAP server issue.

I suggest that it is time to explore other avenues.  A Goggle search identifies slow download as a common issue, possibly with different causes - for example see Error Solved: Why Outlook is so Slow? Best Ways to Speed Up Outlook (stellarinfo.com) 

Other search results mention that users see the emails as being available when using a different email client, supporting the premise that the issue is with the device / Outlook.

Check out the repair .pst file guidance.

What AV are you running?

Does suspending the AV improve matters?

Does running OL in safe mode help? (outlook.exe /safe)

John_B
Hooked
Posts: 8
Thanks: 1
Registered: ‎26-10-2019

Re: Incoming (IMAP) emails intermittently delayed

Hi Townman,

Thank you for your comments. I have been conducting several days of trials based on them.

 

Responses to your questions:-

My Anti-Virus is AVAST-Free. Disabling AV has no obvious effect.

The .ost file is approx. 5GB. I had wondered about its size being significant, but note that the references about being too big generally use 50GB as their yardstick. Thus, my PC’s .ost file  being at 10% of that “limit” suggests size is of no relevance.

Running in Outlook safe mode has no obvious effect. However, there are only a couple of active Add-ons running in “normal mode”, because I generically like to keep all my applications as the base software.

I do not perceive that my PC’s email handling has a performance (as in speed) issue. Speed is the emphasis of many comments on google.com, including your recommended read.  Assembly of, opening, attaching to, saving draft.... all take place at fully acceptable speeds. The actual process of receiving the emails also takes place at fast speed, while sending emails is limited by my Broadband’s uplink speed.

 

Recap of issue:-

There are intermittent periods of failure to receive emails, when I know (e.g. from a loopback  or from Plusnet Webmail) there have been emails waiting for several hours to be delivered to my PC. Currently the problem lasts typically several, as in >4hours, averaging about ten periods per week. However, there are also “clear and good” days.

 

Observations:-

  1. a) During the problem’s periods, I can see from both “screen UI” and “LAN/Internet Data” Router leds, that my PC/Outlook is polling the “IMAP server”, and nothing is being pushed back to my PC, even though there are emails waiting to be delivered to my PC.
  2. b) During a problem period, whether the “poll” was the result of user-action such as changing mail folders or F9, or automatically by the background “5 min” re-synchronisation timer expiring, makes no difference to the success of having the latent emails delivered/advertised/pushed to my PC.

 

Mitigating Factors:-

The two factors which I have identified as having made a significant difference in reducing the impact/occurrence of the problem are:-

  1. a) if after several/many unsuccessful “F9 or Send-Receive-all-folders or 5min sync” polls, I then submit a loopback message of a big size ( e.g. 3MB), then the next “poll” generally results in a bundle of delayed emails arriving along with my 3MB message.
  2. b) updating the IMAP/SMTP port numbers and adding encryption as recommended by you in your earlier post has probably halved the problem.

 

All suggestions welcomed.

 

John_B