exchangelib

Manually specify the EWS server URL and disable autodiscover. You can often find the EWS URL in Outlook's connection settings or through your IT administrator.
```python
from exchangelib import Credentials, Account, Configuration

creds = Credentials(username='your_username@your_domain.com', password='your_password')
config = Configuration(server='your.exchange.server.com', credentials=creds) # e.g., 'outlook.office365.com' or a specific EWS URL
account = Account(primary_smtp_address='your_username@your_domain.com', config=config, autodiscover=False)
```

First, double-check your username and password, including the format (e.g., `DOMAIN\username` vs. `user@domain.com`). If using Office 365, consider switching to OAuth2 authentication as Basic Auth is largely deprecated.
```python
from exchangelib import Credentials, Account, OAUTH2, OAuth2Credentials

# For NTLM/Basic Auth (if supported by your server)
# creds = Credentials(username='DOMAIN\username', password='your_password')

# For Office 365 / OAuth2
# Requires prior Azure AD app registration to get client_id, client_secret, and tenant_id
ocreds = OAuth2Credentials(
    client_id='your_client_id',
    client_secret='your_client_secret',
    tenant_id='your_tenant_id', # or 'organizations' or 'common'
    access_token='your_initial_access_token' # This needs to be refreshed externally
)

account = Account(primary_smtp_address='user@example.com', credentials=ocreds, autodiscover=True, access_type=OAUTH2)
```

To fix this, you can either explicitly trust the certificate by providing its path to `exchangelib` or, as a last resort for testing (not recommended for production), disable SSL verification.
```python
from exchangelib import DELEGATE, Account, Credentials, Configuration
from exchangelib.protocol import BaseProtocol, NoVerifyHTTPAdapter
import ssl

# Option 1: Provide path to CA bundle (recommended)
# BaseProtocol.HTTP_ADAPTER_CLS.ssl_context = ssl.create_default_context(cafile='/path/to/your/ca_bundle.pem')

# Option 2: Disable SSL verification (use with caution, for testing only)
BaseProtocol.HTTP_ADAPTER_CLS = NoVerifyHTTPAdapter

creds = Credentials(username='user@example.com', password='your_password')
account = Account(primary_smtp_address='user@example.com', credentials=creds, autodiscover=True)
```

Always use `exchangelib.EWSTimeZone` and `exchangelib.EWSDateTime` when working with dates and times that will be sent to or received from Exchange.
```python
from exchangelib import EWSDateTime, EWSTimeZone
from datetime import datetime

# Correct way to create a timezone-aware EWSDateTime
tz = EWSTimeZone.localzone() # or EWSTimeZone.timezone('Europe/Copenhagen')
now = EWSDateTime.now(tz=tz)

# If you have a standard datetime object and need to convert it:
standard_dt = datetime.now(tz=pytz.utc) # Example with pytz
ews_tz = EWSTimeZone.from_timezone(standard_dt.tzinfo)
news_dt = EWSDateTime(standard_dt.year, standard_dt.month, standard_dt.day, 
                      standard_dt.hour, standard_dt.minute, standard_dt.second, 
                      tzinfo=news_tz)
```

Ensure `exchangelib` is installed in your environment using pip. If using a virtual environment, activate it first. If deploying with PyInstaller, ensure PyInstaller is correctly configured to include `exchangelib` as a hidden import if necessary.
```bash
pip install exchangelib

# If using PyInstaller and encountering issues, you might need:
pyinstaller --hidden-import exchangelib your_script.py
```