Outlook 2016 - Mails stuck at Outbox

Bronze Contributor

Hi, just wanted to find out if anyone else is having troubles with Outlook 2016 (or other version?) since October 5th or 6th?

I have multiple users with mails stuck in their Outbox and no solution yet. Additionally I'm getting a MAPI Error (mapi 1.0 4c2) for some of those users and Outlook won't start because of it.

Their Mailbox is in O365. I'm not sure if this has anything to do with the latest Office 2016 C2R Version from October.

4 Replies

Hello Ivan,


I saw on a few ocasions that the MAPI Error (mapi 1.0 4c2) was caused by an outdated Salesforce addin.


For the emails stuck in outbox you could try to troubleshoot using OffCAT>Advanced Tools>Real-Time Logging and select the scenario "Message stuck in the outbox"

Hi, yeah I've tried a few things, and came to the following preliminary conclusion.

The latest O2016 C2R version does not like the OpenText Enterprise Connect Addin v10.5.2. Not sure about other verisons though.

I have the same issue with E-Mails stuck in the Outbox. Tried to start Outlook in the safe mode but didn't bring any improvements. I installed the SaRA tool but this also didn't help. I run the quick repair from Office and also didn't help.


If anybody has another solution or try, please let me know. Otherwise I would reinstall Office to see if that would fix the problem.


Thanks in advance

I am having the exact same problem! Messages get stuck in my outbox! Don't get send at all sometimes or take forever to send... every now and then they send... it sucks so bad! I called Microsoft support at least 6 Times and each time we created a new profile. The effect was that it worked for a week or two and then it went bad again.

I mean this 2020, Microsoft and we are talking SENDING E-MAILS with a PAYED-FOR-PROGRAM not Thunderbird, not GMX - they work like a snap! This is what gets me the most...

We have tried with or without firewall and Virus-Software... the issue is only with outlook. On my mac with thunderbird I can send flawlessy...


I am so annoyed by this problem I cannot even find the right words anymore...

PLEASE HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!