IMAP stopped working

[#1]

I use both outlook and an android app to access my email using IMAP.  I have noticed that i have received no email to the outlook client since yesterday afternoon.

I was able using my android app on phone to access the email until about 5 minutes ago, and now when I try and connect I get an error saying "A stable connection to the server could not be established".

I can access webmail fine.

Anyone ese having issues or aware of what may have changed to cause this?

[#2]

That very much sounds like a connection issue - email clients are sensitive to connection time outs, which will not be apparent when using webmail.

How is the rest of your internet browsing?

Is the phone line quiet?

[#3]

All fine, using work internet connection for the outlook 365 connection

Phone is using 4g

Phone wont connect at all now, just keep getting the same error.

interestingly when I use webmail to access the email and delete an email from the inbox (moving it to trash), when I synchronise on the PC, that email appears in the trash folder, but its not updating the inbox to show any mail since yesterday afternoon.

Phone still showing A stable connection to the server could not be established.

[#4]

There is a lot going on in your descriptions ... Office365 ... work internet connection ... 4G connection ... phone.

It would help if you can clarify what devices and email applications you are using.

What does / does not work when connected how.

For example:

1. Phone: iPhone 11 using in built apple-mail
2. PC: Win 11 using Office365 (OL2016)

Connectivity

1. Home on Plusnet (no VPN)
   1. Phone; WiFi connected does not work
   2. PC: Ethernet connected does not work
   3. Webmail on PC - works!
2. Work
   1. Phone WiFi works
   2. PC WiFi works
3. Out and about
   1. Phone 4G works

A profile such as the above would point to a Plusnet network performance / stability issue which can have a marked impact on email performance, whist being not noticeable doing other things, such as browsing the web (e.g. webmail) ... especially if you do not stream / video call.

Broadband is not going to work well if the "phone" line is not working properly.

Please perform a quiet line test - dial 17070 select option 2 using a corded phone plugged into the test socket behind the face plate of the master socket. It should be silent. A noisy phone line (or no dial tone) will have a marked adverse impact on the performance of broadband.

If the line is noisy or there is no dial tone, then a PHONE LINE fault needs to be raised with your phone provider. If this is PlusNet, you can report a fault on line using the button below.  From the Q&A list, choose the one which matches the problem, 'open' the 'section' and click the trouble-shooter link.  NB: If you receive a failure message (rather than a log-in prompt) then log-in to the user portal in a different browser tab and attempt to use the trouble-shooter again.

• Phone Faults

[#5]

Outlook - running on win 10. connected using office fibre connection (not PN).  Mail from office 365 works fine, whole office is working fine with all aspects of web connectivity.

on my outlook application i have my personal plusnet email setup as an additional account, using IMAP.

It has been working flawlessly for months/years.  Stopped receiving new email to the inbox yesterday afternoon.

Phone - android using builtin mail, connected using 4g (we dont have wifi in the office).  Again has been working fine for months.  Was until just a few minutes ago working fine.  Now cant connect and giving the "a stable connection to the server cannot be established".

All other internet activity on the phone works fine using the 4g.

If I log onto webmail (using firefox on office pc) i can see all email.  If i move an email from my inbox to deleted items on webmail, then I perform a forced send receive all folders on my outlook, then that email will appear within the trash folder in my personal account on outlook

i.e. IMAP on outlook (via ofice fibre connection) appears to be syncronising all email folders other than inbox.

mail application on android doesnt want to connect at all.

[#6]

To add further information, it is starting to point to something at PN.

I deleted the imap account from outlook and recreated it.

It connects and begins synchronising, it sets up the folder structure and begins to sync the mail within the folders.  some folders with just a few emails in synchronise OK, some others like inbox & sent fail to have any email appear.  It appears as though the connection to the PN server is either slow or intermittent (via theoffice fibre)

This could/would explain the error being received by the android application using a completely different method of connecting (4G).

[#7]

In respect of outlook, what happened yesterday?  An update?

Try refreshing the IMAP folder subscriptions (right click on the Outlook folder).

Try starting Outlook in safe mode - WinKey+R - outlook.exe /safe

Then try a resync.

If all that fails, try setting the root folder in the account settings to inbox.

[#8]

I shall give that a go tomorrow as I've left the office for the day. Good news is that email started working again on my phone, though only when I got home (PN connection) and tried logging in again.
Perhaps something is afoot with the starttls protocol when connecting using a non PN connection.

Edit, yep that appears to be the case.
Turn off wifi and I cannot connect to imap using 4g and starttls.
Turn wifi back on so using a PN connection and SSL/TLS and it connects fine.

[#9]

Encryption settings…

IMAP / POP3 (inbound) is TLS/SSL

SMTP (outbound) is STARTTLS (port 587)

[#10]

Things appear to be resolving themselves as mobile working fine again over 4G and PN connection.

Outlook also partially resolved.  It appears to be synchronising some folders but not sent or inbox (largest folders).

However using webmail to move all but 200 emails from sent into a temp folder and the sent items syncs, then move the mail now in the temp folder back into sent 200 at a time and it syncs.

Same for inbox.

Seems to be some sort of limitation on the number of mails that IMAP via outlook will synchronise at once.  Perhaps as part of my regular cleanup I deleted more than X emails and this caused outlook to be unable to sync, whatever the value of X is I dont know, but hopefully all returning to normal.

Thanks for your assistance, much appreciated.

[#11]

I would suggest that you just need to give it time ... especially if there are lots of emails to sync.

[#12]

theres "only" 1100 items in sent, but attempting to sync even setting timeout on server to 10 minutes doesnt work.  As soon as there are around 300 ish mails in a folder outlook syncronises the folder in about 20 seconds.   Im guessing it must be a setting or limitation somewhere in either outlook or the office 365 setup.

[#13]

There are two considerations - server time out and resynch interval.

What is the resync interval in the OL send and receive settings?

If that is shorter than the time it is taking to do a big resync on the mailbox, there is a risk that the sync process will be restarted before the previous one finished.

Also try this Find and fix email delivery issues as a Microsoft 365 for business admin - Exchange | Microsoft Lear...

[#14]

curiouser and curiouser...

All now working on PC. but not on android - that wont even log in.

Settings on PC, outlook, IMAP account:

incoming server:  imap.plus.net

Port: 993

Encryption: SSL/TLS

Outgoing:

smtp.plus.net

587

StartTls

Can send mail and receive new mail. All works fine.

Exact same settings on android (whether using built in email app or outlook on android and get various errors from connection timeout (but almost instantly), to password incorrect (it isnt) or "a stable connection could not be established".

Bizzare.

[#15]

Outgoing server should be relay.plus.net to avoid issues with the security certificates.