#66 Error performing SASL authentication step: SASL(-1): generic failure: Unable to find a callback: 18948

[comatory]

I'm using isync on MacOS Monterey installed via homebrew package manager. The version is 1.4.4. One of my accounts suddenly stopped syncing, I don't remember updating anything in my system and I don't remember messing with my authentication settings.

I did however tried creating directory inside one of the maildir folders (stupid I know) but I don't see how that could be related to authentication. I have isync set up on other computer too and I get the same error there now.

When I run mbsync --debug myaccount.com I get this:

Reading configuration file /Users/[user]/.mbsyncrc
Channel myaccount.com
Opening far side store myaccount.com-remote...
F: [ 1] Enter connect_store
Resolving imap.fastmail.com... ok
Connecting to imap.fastmail.com (66.111.4.136:993)...
F: [ 1] Leave connect_store
Opening near side store myaccount.com-local...
N: [ 2] Enter connect_store
N: [ 2] Callback enter connect_store, sts=0
pattern '*' (effective '*'): Path, no INBOX
N: [ 3] Enter list_store, flags=2
N: [ 3] Callback enter list_store 
[list of my folders is printed here]
N: [ 3] Callback leave list_store
N: [ 3] Leave list_store
N: [ 2] Callback leave connect_store
N: [ 2] Leave connect_store
Connection is now encrypted
F: * OK IMAP4 ready
F: >>> 1 CAPABILITY
F: * CAPABILITY IMAP4 IMAP4rev1 LITERAL+ ENABLE UIDPLUS SASL-IR NAMESPACE CONDSTORE SORT LIST-EXTENDED QRESYNC MOVE SPECIAL-USE CREATE-SPECIAL-USE IDLE AUTH=PLAIN AUTH=LOGIN AUTH=XOAUTH2 AUTH=OAUTHBEARER
F: 1 OK completed
Logging in...
Authenticating with SASL mechanism OAUTHBEARER...
Error performing SASL authentication step: SASL(-1): generic failure: Unable to find a callback: 18948
F: [ 1] Callback enter connect_store, sts=3
F: [ 4] Enter cancel_cmds
F: [ 4] Callback enter cancel_cmds
F: Enter free_store
F: Leave free_store
F: [ 4] Callback leave cancel_cmds
F: [ 4] Leave cancel_cmds
N: [ 5] Enter cancel_cmds
N: [ 5] Callback enter cancel_cmds
N: Enter free_store
N: Leave free_store
N: [ 5] Callback leave cancel_cmds
N: [ 5] Leave cancel_cmds
F: [ 1] Callback leave connect_store

My configuration file for the account looks like this:

IMAPAccount myaccount.com
Host imap.fastmail.com
User user@myaccount.com
PassCmd "gpg --decrypt --no-tty ~/mail/myaccount.com.gpg"
SSLType IMAPS
SSLVersions TLSv1.2
Port 993

IMAPStore myaccount.com-remote
Account myaccount.com

MaildirStore myaccount.com-local
SubFolders Verbatim
Path ~/mail/myaccount.com/
Inbox ~/mail/myaccount.com/INBOX

Channel myaccount.com
CopyArrivalDate yes
Far :myaccount.com-remote:
Near :myaccount.com-local:
Patterns "*"
Sync All
Create Both
Expunge Both
SyncState *

[Oswald Buddenhagen]

you presumably need AuthMech LOGIN.
though that may stop working at some point, and you'll need to make XOAUTH2 work (there are various related threads in the mailing list archive).

[comatory]

@ossi Thank you very much for the quick response. So this is probably related to changes on my email provider's (Fastmail) side?

Why AuthMech might stop working at some point? Sorry I don't know what AuthMech or X0AUTH2 mean so just trying to research what I should actually do to fix this.

[Oswald Buddenhagen]

So this is probably related to changes on my email provider's (Fastmail) side?

yes

Why AuthMech might stop working at some point?

because providers increasingly migrate away from password authentication.

I don't know what [...]

the man page and google provide all the answers.

[comatory]

Ok "solved" by adding Login to AuthMechs field in configuration file.