This Log may  help 


org.kde.kgapi: Received reply from QUrl("https://accounts.google.com/o/oauth2/token")
org.kde.kgapi: Status code:  200
org.kde.kgapi.raw: "{\n  \"access_token\" : \"ya29.Gly9BZxpkmSb6XL8PE4jz8Qw24AjK8WlFyQCyd1NC4pxMuVNvT6uPdwtkqVj95yWBLUrPzjNzLkbuk7wuTriOK084tUoK4vvA9Mi0czk146hajEEUkSK1UPS68M6uA\",\n  \"expires_in\" : 3600,\n  \"id_token\" : \"eyJhbGciOiJSUzI1NiIsImtpZCI6ImE3NDhlOWY3NjcxNTlmNjY3YTAyMjMzMThkZTBiMjMyOWU1NDQzNjIifQ.eyJhenAiOiI1NTQwNDE5NDQyNjYuYXBwcy5nb29nbGV1c2VyY29udGVudC5jb20iLCJhdWQiOiI1NTQwNDE5NDQyNjYuYXBwcy5nb29nbGV1c2VyY29udGVudC5jb20iLCJzdWIiOiIxMTQzMDUxMzU0MDQyMDEwMDA5NjMiLCJlbWFpbCI6ImR1Ym9pcy5taWNoZWxAZ21haWwuY29tIiwiZW1haWxfdmVyaWZpZWQiOnRydWUsImF0X2hhc2giOiJYYmlmeDR0eHFYeUJUQ0NrQ3RFRm9nIiwiZXhwIjoxNTI2NDc0MTg1LCJpc3MiOiJhY2NvdW50cy5nb29nbGUuY29tIiwiaWF0IjoxNTI2NDcwNTg1fQ.pgkJQb807Mha4K2KDrBdFzT4CBefr_QD_Cd2l3y0QKfO2-g5YxaUEEGy0fSIlEpyEMzboiZAKk_g8eyFmNDFSu8Xn6fazrcC-eYmClhiZG4j8wDrJhIEBeBWWKlGK9arySLAsr3jRlH6fMC9cMMMdRHvHgayQ1Kb3oM-3gq0w8WljtboEK9rWqscm9vm0T1yrXN-nk-_H1_9vlo3DtbPKgArXpNYhg20UGiP3af8SW0kwLfMtx-zmnF74iZhT1VYS23qASeWDV_m7HfdNATYptWSbTdvzApc7uYaPQuMP9hFyPN_yx6NSoz1BgP55_-fDvjqRqswRsuuasGG-VYEig\",\n  \"token_type\" : \"Bearer\"\n}"
org.kde.kgapi: 
qt.network.ssl: QSslSocket::startClientEncryption: cannot start handshake on non-plain connection
org.kde.pim.kimap: Connection to server lost  0
org.kde.pim.imapresource: Session login cancelled
[SASL-XOAUTH2] - Requesting authID![SASL-XOAUTH2] - Requesting token
![SASL-XOAUTH2] - filling prompts
![SASL-XOAUTH2] - Requesting authID![SASL-XOAUTH2] - Requesting token
!user=acme_user@gmail.comauth=Bearer ya29.Gly8BTtdidTWvNGCxiLmYI3Pv-o1qCIwbrC82DBR9t3DvMMx6Ei9ZZspkxHhxHnJHssSHv0TJ326S5fi11BSkzixbQb8QGqPqSHfT-ple7CQxKpvkeLgfCa5qF13CQuser=acme_user@gmail.comauth=Bearer ya29.Gly8BetseYEZFFAs8oJftuLHakAP5MF_Yw2onNGGAKmp-Jl6TL3wb-102hYj_i-YTnhy3OkG3yQBVbUJRaDt79fFFtr90EW4F7FI5PvQByPMMRDgsH-jpjuXShUDJwuser=acme_user@gmail.comauth=Bearer ya29.Gly8BetseYEZFFAs8oJftuLHakAP5MF_Yw2onNGGAKmp-Jl6TL3wb-102hYj_i-YTnhy3OkG3yQBVbUJRaDt79fFFtr90EW4F7FI5PvQByPMMRDgsH-jpjuXShUDJwuser=acme_user@gmail.comauth=Bearer ya29.Gly8BetseYEZFFAs8oJftuLHakAP5MF_Yw2onNGGAKmp-Jl6TL3wb-102hYj_i-YTnhy3OkG3yQBVbUJRaDt79fFFtr90EW4F7FI5PvQByPMMRDgsH-jpjuXShUDJwuser=acme_user@gmail.comauth=Bearer ya29.Gly8BetseYEZFFAs8oJftuLHakAP5MF_Yw2onNGGAKmp-Jl6TL3wb-102hYj_i-YTnhy3OkG3yQBVbUJRaDt79fFFtr90EW4F7FI5PvQByPMMRDgsH-jpjuXShUDJwuser=acme_user@gmail.comauth=Bearer ya29.Gly9BZxpkmSb6XL8PE4jz8Qw24AjK8WlFyQCyd1NC4pxMuVNvT6uPdwtkqVj95yWBLUrPzjNzLkbuk7wuTriOK084tUoK4vvA9Mi0czk146horg.kde.pim.imapresource: Expunge failed:  "Échec de Purger. Le serveur a répondu : A000065 NO mailbox selected READ-ONLY "
org.kde.pim.imapresource: Expunge failed:  "Échec de Purger. Le serveur a répondu : A000161 NO mailbox selected READ-ONLY "
[SASL-XOAUTH2] - Requesting authID![SASL-XOAUTH2] - Requesting token
![SASL-XOAUTH2] - filling prompts
![SASL-XOAUTH2] - Requesting authID![SASL-XOAUTH2] - Requesting token
!org.kde.pim.akonadicore: The item sync is being rolled-back.
QIODevice::write (KTcpSocket): device not open
org.kde.pim.kimap: Connection to server lost  0
org.kde.pim.imapresource: Session login cancelled
org.kde.pim.kimap: Connection to server lost  0
org.kde.pim.imapresource: Session login cancelled

I restarted kwallet and akonadidb for get an issue.

I started manually knetwork manger from the KDE menu. (kwalletmanager5)
I removed the Google key 

I checked The processus I noted name changed 
:~$ ps -aef | grep kwal
users  13282     1  0 08:51 ?        00:00:00 /usr/bin/kwalletd5

I restarted akondictl 
Kamil connection seems working better.

Could you please verify the status of this bug? Is it resolved for you, or are you waiting for a developer to investigate this issue?

Hi Christoph, 

Thank for responding and supporting

I don't know if the problem will come back yet. In this case I should reopen the case as there is a bug somewhere else.

Thank

The access to GMAIL in IMAP mode still very slow with KMail 5.7.3
It's not possible to word with this software anymore. Since 5 years, I worked without problem with Kmail.

Could you give any advice ?

org.kde.pim.akonadicore: Creating/updating items from the akonadi database failed: "Erreur inconnue."
org.kde.pim.akonadicore: "Erreur inconnue."
org.kde.pim.akonadicore: Creating/updating items from the akonadi database failed: "Multiple merge candidates, aborting"
"Item query returned empty result set"
"Item query returned empty result set"
"Item query returned empty result set"
QIODevice::write (KTcpSocket): device not open
org.kde.pim.imapresource: Expunge failed:  "Échec de Purger. Le serveur a répondu : A000005 NO mailbox selected READ-ONLY "
org.kde.pim.imapresource: Expunge failed:  "Échec de Purger. Le serveur a répondu : A000101 NO mailbox selected READ-ONLY "
org.kde.pim.akonadiserver: Handler exception: Unable to fetch item from backend (collection -1) : Unable to retrieve item from resource: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
org.kde.pim.akonadiserver: Handler exception: Unable to fetch item from backend (collection -1) : Unable to retrieve item from resource: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.

I've got MySQL error like : 

2018-05-22T11:26:04.039264Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without certificate and private key
2018-05-22T11:26:04.062854Z 0 [Warning] Insecure configuration for --pid-file: Location '/tmp' in the path is accessible to all OS users. Consider choosing a different directory.
2018-05-22T11:26:04.090710Z 0 [ERROR] Incorrect definition of table performance_schema.replication_connection_status: expected column 'RECEIVED_TRANSACTION_SET' at position 7 to have type longtext, found type text.
2018-05-22T11:26:04.091222Z 0 [ERROR] Incorrect definition of table performance_schema.replication_group_member_stats: expected column 'COUNT_TRANSACTIONS_ROWS_VALIDATING' at position 6, found 'COUNT_TRANSACTIONS_VALIDATING'.
2018-05-22T11:26:04.093699Z 0 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.7.22-0ubuntu18.04.1'  socket: '/tmp/akonadi-mdubois.1tEWqn/mysql.socket'  port: 0  (Ubuntu)
2018-05-22T11:26:04.135431Z 0 [Note] InnoDB: Buffer pool(s) load completed at 180522 13:26:04

I doubt this is a KWallet problem. Reassigning to Akonadi developers for inspection.

Thanks Christoph

I refreshed the Google application authorization and I reinstalled my google "imap" account. I seems to work now. I'm going to follow the use. this problem make me a few crazy as I need to read my mail and kept the organization of the thing I'm kepting local

Kmail worked fine yesterday. 
Today it's not working well 
Akonadi log : 
![SASL-XOAUTH2] - Requesting authID![SASL-XOAUTH2] - Requesting token
!org.kde.pim.kimap: sasl_client_step failed with: -1 "SASL(0): successful result: "
org.kde.kgapi.raw: Requesting token refresh:  "client_id=xxxxxxxxxxxxxx6.apps.googleusercontent.com&client_secret=mdT1DjzohxN3npUUzkENT0gO&refresh_token=1/fnxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxaG9hcn_MlArNBs&grant_type=refresh_token"
org.kde.kgapi: Queued QUrl("https://accounts.google.com/o/oauth2/token")
org.kde.kgapi: KGAPI2::AuthJob(0x7f6628031250) Dispatching request to QUrl("https://accounts.google.com/o/oauth2/token")
org.kde.kgapi.raw: "client_id=xxxxxxxxxxxxxxxx66.apps.googleusercontent.com&client_secret=mdTxxxxxxxxxxxxxxxxxxxxxxxxxxx&refresh_token=1/fnMxxxxxxxxxxxxxxxxxxxxxxxxxxxcn_MlArNBs&grant_type=refresh_token"
org.kde.kgapi: Received reply from QUrl("https://accounts.google.com/o/oauth2/token")
org.kde.kgapi: Status code:  200
org.kde.kgapi.raw: "{\n  \"access_token\" : \"ya29.GlzEBcvQuxtugaZxJWqTdO-m17pYFdZwN6xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxp3tKtMJUWdI_0jlauudnaNZQv9Ge2xxxxxxxxxxxxxxxxxxxxxx8Td9Q\",\n  \"expires_in\" : 3600,\n  \"id_token\" : \"eyJhbGciOiJSUzI1NiIsImtpZCI6IjAyOWYyNjlmM2YwNmFmMWU5M2RhYzY3MDYzOTc3ZjcxM2E3N2YxOWUifQ.eyJhenAiOixxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxNTI3MDM4NDcwfQ.o_BcrxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxBedvKxGRSkHFZsGB9WrY2-Kxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx8_deqtDdFq3zPfQ_Hq5PmpBaQc0I-GXEYAMbCtjA9tZHxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxRY1lzlWTECzGD6s4ctV0S49Ppb0cn3U6wEbp_M-1cTxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxBX-8v6vdqu-dYheRxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxYZ8CNPyD_jfGisnwoam3C9k61avNYq47vg\",\n  \"token_type\" : \"Bearer\"\n}"
org.kde.kgapi: 
qt.network.ssl: QSslSocket::startClientEncryption: cannot start handshake on non-plain connection
org.kde.pim.kimap: Connection to server lost  0
org.kde.pim.imapresource: Session login cancelled
org.kde.pim.imapresource: Expunge failed:  "Échec de Purger. Le serveur a répondu : A000005 NO mailbox selected READ-ONLY "
Tokenizer Warning: 8Bit character ' ð '
Tokenizer Warning: 8Bit character '  '
Tokenizer Warning: 8Bit character '  '

Kmail seems working with my last google configuration of my account. 
However I did three times the operation.
I m going to wait before to use kontact.