[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  * OK The Microsoft Exchange IMAP4 service is ready. [QWxhZGRpbjpvcGVuIHNlc2FtZQ==]
[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  IUR0 CAPABILITY
[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  * CAPABILITY IMAP4 IMAP4rev1 AUTH=PLAIN AUTH=XOAUTH2 SASL-IR UIDPLUS MOVE ID UNSELECT CHILDREN IDLE NAMESPACE LITERAL+
[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  IUR0 OK CAPABILITY completed.
IMAPS: AUTH: PLAIN
IMAPS: AUTH: XOAUTH2
IMAPS: protocolConnect login, host=outlook.office365.com, user=user_name@atl.onmicrosoft.com, password=<non-null>
IMAPS: AUTHENTICATE PLAIN command trace suppressed
IMAPS: AUTHENTICATE PLAIN command result: IUR1 NO AUTHENTICATE failed.
IMAPS: trying to connect to host "outlook.office365.com", port 993, isSSL true
[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  * OK The Microsoft Exchange IMAP4 service is ready. [QWxhZGRpbjpvcGVuIHNlc2FtZQ==]
[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  IUS0 CAPABILITY
[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  * CAPABILITY IMAP4 IMAP4rev1 AUTH=PLAIN AUTH=XOAUTH2 SASL-IR UIDPLUS ID UNSELECT CHILDREN IDLE NAMESPACE LITERAL+
[Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  IUS0 OK CAPABILITY completed.
IMAPS: AUTH: PLAIN
IMAPS: AUTH: XOAUTH2
IMAPS: protocolConnect login, host=outlook.office365.com, user=user_name@atl.onmicrosoft.com, password=<non-null>
IMAPS: AUTHENTICATE PLAIN command trace suppressed
IMAPS: AUTHENTICATE PLAIN command result: IUS1 NO AUTHENTICATE failed. 

 WARN [Alerts Incident] Caesium-1-3 anonymous    Incident ITSM  Incident ITSM [10900]: javax.mail.AuthenticationFailedException: AUTHENTICATE failed. while connecting to host "outlook.office365.com" as user "user_name@atl.onmicrosoft.com" via protocol "SECURE_IMAP": javax.mail.AuthenticationFailedException: AUTHENTICATE failed.
javax.mail.AuthenticationFailedException: AUTHENTICATE failed.
	at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:708) [jakarta.mail-1.6.5.jar:1.6.5]
	at javax.mail.Service.connect(Service.java:364) [jakarta.mail-1.6.5.jar:1.6.5]
	at javax.mail.Service.connect(Service.java:222) [jakarta.mail-1.6.5.jar:1.6.5]
	at javax.mail.Service.connect(Service.java:243) [jakarta.mail-1.6.5.jar:1.6.5]
	at com.atlassian.mail.server.InternalAuthenticationContext.connectService(InternalAuthenticationContext.java:58) [atlassian-mail-5.0.3.jar:?]
	at com.atlassian.mail.server.AbstractMailServer.smartConnect(AbstractMailServer.java:156) [atlassian-mail-5.0.3.jar:?]
	at com.atlassian.jira.service.services.mail.MailServicesHelper.lambda$connectUsing$2(MailServicesHelper.java:81) [jira-api-8.13.3.jar:?]
	at java.util.Optional.map(Optional.java:215) [?:1.8.0_181]
	at com.atlassian.jira.service.services.mail.MailServicesHelper.handleAuthAwareMailServer(MailServicesHelper.java:52) [jira-api-8.13.3.jar:?]
	at com.atlassian.jira.service.services.mail.MailServicesHelper.getConnectedStore(MailServicesHelper.java:46) [jira-api-8.13.3.jar:?]
	at com.atlassian.jira.service.services.mail.MailFetcherService.getConnectedStore(MailFetcherService.java:397) [jira-api-8.13.3.jar:?]
	at com.atlassian.jira.service.services.mail.MailFetcherService$MessageProviderImpl.getAndProcessMail(MailFetcherService.java:166) [jira-api-8.13.3.jar:?]
	at com.atlassian.jira.service.services.mail.MailFetcherService.processMessages(MailFetcherService.java:361) [jira-api-8.13.3.jar:?]
	at com.atlassian.jira.service.services.mail.MailFetcherService.runImpl(MailFetcherService.java:353) [jira-api-8.13.3.jar:?]
	at com.atlassian.jira.service.services.file.AbstractMessageHandlingService.run(AbstractMessageHandlingService.java:229) [jira-api-8.13.3.jar:?]
	at com.atlassian.jira.service.JiraServiceContainerImpl.run(JiraServiceContainerImpl.java:68) [classes/:?]
	at com.atlassian.jira.service.ServiceRunner.runService(ServiceRunner.java:62) [classes/:?]
	at com.atlassian.jira.service.ServiceRunner.runServiceId(ServiceRunner.java:44) [classes/:?]
	at com.atlassian.jira.service.ServiceRunner.runJob(ServiceRunner.java:32) [classes/:?]
	at com.atlassian.scheduler.core.JobLauncher.runJob(JobLauncher.java:134) [atlassian-scheduler-core-3.0.0.jar:?]
	at com.atlassian.scheduler.core.JobLauncher.launchAndBuildResponse(JobLauncher.java:106) [atlassian-scheduler-core-3.0.0.jar:?]
	at com.atlassian.scheduler.core.JobLauncher.launch(JobLauncher.java:90) [atlassian-scheduler-core-3.0.0.jar:?]
	at com.atlassian.scheduler.caesium.impl.CaesiumSchedulerService.launchJob(CaesiumSchedulerService.java:435) [atlassian-scheduler-caesium-3.0.2.jar:?]
	at com.atlassian.scheduler.caesium.impl.CaesiumSchedulerService.executeClusteredJob(CaesiumSchedulerService.java:430) [atlassian-scheduler-caesium-3.0.2.jar:?]
	at com.atlassian.scheduler.caesium.impl.CaesiumSchedulerService.executeClusteredJobWithRecoveryGuard(CaesiumSchedulerService.java:454) [atlassian-scheduler-caesium-3.0.2.jar:?]
	at com.atlassian.scheduler.caesium.impl.CaesiumSchedulerService.executeQueuedJob(CaesiumSchedulerService.java:382) [atlassian-scheduler-caesium-3.0.2.jar:?]
	at com.atlassian.scheduler.caesium.impl.SchedulerQueueWorker.executeJob(SchedulerQueueWorker.java:66) [atlassian-scheduler-caesium-3.0.2.jar:?]
	at com.atlassian.scheduler.caesium.impl.SchedulerQueueWorker.executeNextJob(SchedulerQueueWorker.java:60) [atlassian-scheduler-caesium-3.0.2.jar:?]
	at com.atlassian.scheduler.caesium.impl.SchedulerQueueWorker.run(SchedulerQueueWorker.java:35) [atlassian-scheduler-caesium-3.0.2.jar:?]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181]

For Google, we recommend using the https://mail.google.com/ scope for IMAP and POP3.

For Microsoft, we recommend https://outlook.office.com/IMAP.AccessAsUser.All or https://outlook.office.com/POP.AccessAsUser.All, and offline_access.