Chamber of horrors: Unknown server responses about android-sms HOT 3 OPEN

I'll misuse this issue as a chamber of horrors for all unknown server responses.

D/InetAddress( 1806): imap.gmail.com: 74.125.47.111 (family 2, proto 6)
D/InetAddress( 1806): imap.gmail.com: 74.125.47.109 (family 2, proto 6)
I/SmsSync ( 1806): Label 'SMS' does not exist yet. Creating.
I/SmsSync ( 1806): 
I/SmsSync ( 1806): 
tv.studer.smssync.SmsSyncService$AuthenticationErrorException: #6# [NO, 
Unknown, Mailbox:, SMS, [Failure]]
I/SmsSync ( 1806): at 
tv.studer.smssync.SmsSyncService.sync(SmsSyncService.java:268)
I/SmsSync ( 1806): at 
tv.studer.smssync.SmsSyncService.access$2(SmsSyncService.java:213)
I/SmsSync ( 1806): at 
tv.studer.smssync.SmsSyncService$1.run(SmsSyncService.java:132)
I/SmsSync ( 1806): Caused by: 
com.android.email.mail.store.ImapStore$ImapException: #6# [NO, Unknown, 
Mailbox:, SMS, [Failure]]
I/SmsSync ( 1806): at 
com.android.email.mail.store.ImapStore$ImapConnection.executeSimpleCommand(ImapS
tore.java:1219)
I/SmsSync ( 1806): at 
com.android.email.mail.store.ImapStore$ImapConnection.executeSimpleCommand(ImapS
tore.java:1206)
I/SmsSync ( 1806): at 
com.android.email.mail.store.ImapStore$ImapFolder.open(ImapStore.java:345)
I/SmsSync ( 1806): at 
tv.studer.smssync.SmsSyncService.sync(SmsSyncService.java:266)
I/SmsSync ( 1806): ... 2 more
I/ActivityManager(   52): Stopping service: tv.studer.smssync/.SmsSyncService

The [NO, Unknown, Mailbox:, SMS, [Failure]] exception in comment 1 happened 
when the "SMS" label was hidden 
for IMAP in the Gmail settings. Switching it to visible fixed it.

Received another report from a user who switched the Android build and was 
unable to use SMS Backup. The 
error message is [NO, Unknown, Mailbox:, Gtexts, [Failure]] (same as above) but 
"Gtexts" label was already visible 
in IMAP.